Nonlinear optical element and process for the preparation of same

ABSTRACT

The present invention provides a nonlinear optical element having a sufficient thickness that can be used as a thin film insusceptible to crack and a process for the preparation thereof. A novel nonlinear optical element which gives a nonlinear response to incident light is provided, comprising finely divided grains of a semiconductor or metal, which grains have been separated out with the reaction of a functional group in a matrix-forming substance containing said functional group, dispersed in a matrix. A process for the preparation of a nonlinear optical element which gives a nonlinear response to incident light is also provided, which comprises mixing a solution of a matrix-forming substance containing a functional group with a metal, a semiconductor or a precursor thereof to form a uniform solution, and then allowing said functional group to undergo reaction to form a matrix while allowing finely divided grains of said metal or semiconductor to be separated out in said matrix.

FIELD OF THE INVENTION

The present invention relates to a nonlinear optical element comprisingfinely divided grains of a semiconductor or metal exerting a nonlinearoptical effect incorporated therein and a process for the preparationthereof. More particularly, the present invention relates to a nonlinearoptical element comprising finely divided grains of a semiconductor ormetal exerting a quantum sizing effect, which grains have been dispersedand separated out in a medium obtained by the hydrolysis of a highmolecular organic compound, or a silane compound by sol-gel method, orin a mixture medium thereof and a process for the preparation thereof.

BACKGROUND OF THE INVENTION

With the development of data processing, a search has been made formaterials exerting a great nonlinear optical effect for the purpose ofrealizing an optical theory element or optical switch on the basis ofwhich photocomputers are developed. As nonlinear optical materials therehave heretofore been known inorganic ferroelectric materials such asLiNbO₃, BaTiO₃ and KH₂ PO₄, quantum well structure semiconductorscomprising GaAs, etc., organic single crystals such as4'-nitrobenzylidene-3-acetamino-4-methoxyaniline (MNBA) and2-methyl-4-nitroaniline (MNA), conjugated organic high molecularcompounds such as polydiacetylene and polyarylene vinylene, andsemiconductor grain-dispersed glass comprising CdS, CdSSe, etc.dispersed in glass.

In particular, extensive studies have been made on semiconductorgrain-dispersed glass as a favorable nonlinear optical material whichexhibits both a high nonlinear optical susceptibility and a highresponse since Jain and Lind discovered in 1983 that a so-called colorglass filter comprising semiconductor grains dispersed in glass exhibitsa high three-dimensional nonlinear optical effect as described in J.Opt. Soc. Am., 73, 647 (1983).

The preparation of this kind of glass has been normally accomplished bya so-called melt-quenching method which comprises heat-melting a mixtureof a powder of glass as a dispersant or starting material thereof and apowder of starting material of semiconductor or metal to make a glassmelt, quenching the glass melt to around room temperature by casting ona metal plate or the like or like means to obtain a supercooled glasssolid solution comprising semiconductor constituent elements dissolvedtherein as ions, and then subjecting the solid solution again to heattreatment at a proper temperature for a predetermined period of time toallow semiconductor grains to be separated out.

However, this method is disadvantageous in that it requires the startingmaterial of semiconductor to be heated to a temperature as high as notlower than 1,000° C. where the material can undergo decomposition orevaporation, limiting the kind of applicable semiconductors and theamount of semiconductor to be added. This prevents the realization of amaterial having a higher nonlinear optical effect for practical use.

As other methods there have been proposed a method which comprises theuse of glass or SiO₂ and an element semiconductor polycrystal such asCdS and CdT as a target in sputtering process to prepare a semiconductorgrain-dispersed glass (as disclosed in J. Appl. Phys., 63 (3), 957(1988), JP-A-2-307832), etc.

Further, an alternate method has been proposed which comprises the useof a high molecular compound as a matrix other than glass in a gas phaseprocess such as vacuum metallizing to disperse finely divided grains ofa semiconductor in the high molecular compound (as disclosed inJP-A-3-119326 and JP-A-3-140335). The gas phase process enablesintroduction of a large amount of semiconductor as compared to theabove-mentioned melt-quenching method. In production of either inorganicmatrix or organic matrix, the apparatus used for the gas phase processis expensive, and the speed of film formation is small so that it issuitable for formation of thin films but not thick films. Thus, the thusobtained element cannot be thick, resulting in limited applications.

As an approach for eliminating these difficulties there has beenproposed a method which comprises dispersing and maintaining finelydivided grains of a semiconductor or metal in a silica gel matrix formedby sol-gel method so that a semiconductor grain-dispersed glass can beprepared at a low temperature.

Examples of such a method include a method which comprises dispersingfinely divided grains of a semiconductor prepared by CVD process or thelike in a hydrolyzable solution of silicon alkoxide (sol), and thengelatinizing the sol so that the finely divided grains of asemiconductor are fixed in glass (as disclosed in JP-A-2-271933 (Theterm "JP-A" as used herein means an "unexamined published Japanesepatent application")), a method which comprises adding finely dividedgrains of a semiconductor to a sol containing a silane coupling agent orallowing the finely divided grains to be separated out in the sol, andthen gelatinizing the sol so that the finely divided grains are fixatedin glass (as disclosed in JP-A-3-199137), and a method which comprisesforming a silica gel containing cadmium acetate, and then reactingcadmium acetate with hydrogen sulfate gas to allow cadmium sulfategrains to be separated out in the silica gel to obtain a semiconductorgrain-dispersed glass as disclosed in the proceedings of The CeramicSociety of Japan's 1989 Annual Conference, lecture No. 2F20, J.Non-Cryst. Solids, 122, 101(1990)!.

However, tetralkoxysilane used in the conventional sol-gel process caneasily crack at the stage of drying the gel. Tetralkoxysilane is alsodisadvantageous in that it cannot give a sufficient film thickness if itis formed into a thin film on a substrate to make an element. In orderto obtain a film thickness enough for element, an approach has beenemployed which comprises repeating the steps of coating a substrate witha thin film to a thickness of not more than about 0.1 μm, and thencalcining the film at a temperature of hundreds of degrees C. to give anappropriate film thickness.

Further, if as a method for dispersing finely divided grains of asemiconductor in a silica gel matrix formed by sol-gel process there isa method which comprises preparing finely divided grains of asemiconductor by separate methods, and then dispersing the finelydivided grains in a sol, it disadvantageous in that the addition of theprocedure for the preparation of the finely divided grains of asemiconductor complicates the process. It is also disadvantageous inthat the finely divided grains used have a grain diameter as small asnot more than hundreds of nanometer and thus can be hardly handled,giving an undesirable factor in the preparation process. These finelydivided grains can easily agglomerate and thus can be hardly disperseduniformly in the medium.

JP-A-2-271933 describes that the dispersion of finely divided grains canbe effectively improved by ultrasonic dispersion or the addition of asurface active agent. However, ultrasonic dispersion inevitably involvesthe agglomeration of finely divided grains during the coating and dryingin the formation of a thin film. The latter approach is disadvantageousin that the surface active agent thus added is decomposed or volatilizedduring the heat treatment, causing the re-agglomeration of finelydivided grains.

In this respect, JP-A-3-199137 discloses the use of a silane couplingagent instead of surface active agent in an attempt to solve the problemof agglomeration of finely divided grains. In this approach, the silanecoupling agent acts like a surface active agent and undergoes hydrolysisto connect to a matrix, making the material thermally stable andrelatively undecomposable. JP-A-3-199137 proposes as a method forsolving the problem of handling finely divided grains of a semiconductorto be added to a sol a method which comprises adding finely dividedgrains of a semiconductor in the form of solution to a sol, and thenforming finely divided grains of a semiconductor in the sol with the aidof a solution of a paired ion source or reactive gas. However, thismethod is disadvantageous in that the finely divided grains thusseparated out have a difficulty of diffusion, making it difficult toallow finely divided grains of a semiconductor having a quantum sizeeffect to be uniformly separated out. Thus, the effect of this methodleaves much to be desired.

Unlike the foregoing method, a method which comprises preparing a gelsolid containing semiconductor material ions, and then subjecting thegel solid to post-treatment with hydrogen sulfate gas or the like toallow finely divided grains of a semiconductor to be separated out haveno problems of complicated specification due to handling of finelydivided grains or no difficulty of diffusion. However, since this methodrequires the use of a highly toxic gas such as hydrogen sulfate, itgives a very dangerous working atmosphere that requires a complicatedprocess for safety. In the process which comprises post-treatment toallow finely divided grains to be separated out, as a starting materialof finely divided grains of a semiconductor or metal there may be used amaterial soluble in a reactive medium which is then uniformly dissolvedin a solution so that finely divided grains can be uniformly separatedout in the medium. However, some materials have no proper solvent,limiting the concentration of finely divided grains which can be added.

Sol-gel method is a low-temperature process compared withmelt-quenching, however, it requires to heat to a temperature of about600° C. Therefore, more low-temperature process is required to solve theproblems such as decomposition of a semiconductor material by heating.

On the other hand, studies have been made on finely divided grains of asemiconductor or metal having a nonlinear optical effect. In particular,extensive studies have been made on the use of finely divided grains ofcuprous halide which have excitons having a small Bohr diameter that canbe effectively confined to give a great three-dimensional nonlinearoptical effect (as described in Journal of Non-Crystalline Solids,134(1991), pp. 71-76, Journal of American Ceramic Society, 74(1991), pp.238-240, Journal of Chemistry Society of Japan, No. 10 (1992), pp.1231-1236). These cuprous halides are not soluble in a silane compoundsuch as tetraethoxysilane Si(OCH₂ CH₃)₄ !, which has been heretoforeused as a starting material of medium. Thus, the solvents in which thesecuprous halides are soluble are limited. Further, since these cuproushalides have a low solubility, the amount of these cuprous halides whichcan be uniformly dissolved in a sol is low, making it impossible toallow finely divided grains to be separated out in a high concentrationin a gel as a product. In general, the higher the concentration offinely divided grains to be added is, the higher can be expected thenonlinear optical effect. For the purpose of obtaining a materialexerting a high nonlinear optical effect, a method has been sought foradding cuprous halides in a high density.

Further, if an easily oxidizable material such as cuprous halide isseparated out, it undergoes deterioration such as oxidation anddecomposition in a sol or during heat deposition, making it difficult todope the sol with such a material.

SUMMARY OF THE INVENTION

It is thus an object of the present invention to provide a nonlinearoptical element which has an enough thickness and can be used as a thinfilm insusceptible to crack.

It is another object of the present invention to provide a nonlinearoptical element which exhibits excellent workability for the formationof an element, mechanical strength, environmental resistance and storagestability.

It is a further object of the present invention to provide a nonlinearoptical element comprising a matrix having finely divided grains of asemiconductor or metal dispersed and retained uniformly therein in ahigh concentration and enabling these finely divided grains to fullyattain their functions.

It is a still further object of the present invention to provide aprocess for the preparation of a nonlinear optical element which enablesan easy preparation of the foregoing nonlinear optical element by meansof a simple apparatus in a low temperature.

These and other objects of the present invention will become moreapparent from the following detailed description and examples.

The inventors made extensive studies on a material which forms a mediumhaving finely divided grains of a semiconductor or metal dispersed andretained therein. As a result, it was found that any material whichenables a semiconductor or metal component incorporated therein to beseparated out in the form of finely divided grains by heat treatment orchemical treatment, even though it is an organic high molecular materialnot to mention a high molecular inorganic material, can be used as amatrix of nonlinear optical element, i.e., can be formed into a thinfilm having a thickness enough for such an element. Thus, the presentinvention has been worked out.

The foregoing objects of the present invention are accomplished with anonlinear optical element which gives a nonlinear response to incidentlight, comprising finely divided grains of a semiconductor or metal,which grains have been separated out with the reaction of a functionalgroup in a matrix-forming substance containing the functional group,dispersed in a matrix.

The foregoing objects of the present invention are also accomplished bya process for the preparation of a nonlinear optical element which givesa nonlinear response to incident light, which comprises mixing asolution of a matrix-forming substance containing a functional groupwith a metal, a semiconductor or a precursor thereof to form a uniformsolution, and then allowing said functional group to undergo reaction toform a matrix while allowing finely divided grains of said metal orsemiconductor to be separated out in said matrix, i,e., reducing oreliminating an interaction between the functional group and the metal,semiconductor or precursor thereof to separate out in situ by way of afunctional reaction. After the functional reaction for precipitation ofthe fine grains, the grain-forming compounds may be chemically modifiedby reduction with a reducing agent (e.g., hydrogen, sodium borohydride)or by a reaction with sulfides (e.g., hydrogen sulfide, sodium sulfide).The matrix-forming substance having a functional group contains at leastone high or low molecular compound having a functional and is capable offorming a matrix. Namely, the matrix-forming substance is a substancecapable of forming an inorganic high molecular compound, or an organichigh or low molecular compound in the resulting matrix upon thefunctional reaction and of constituting the composition of the finalmatrix other than the fine grains of metal or semiconductor. In the casewhere the substance having a functional groups is capable of providing afinal matrix having a sufficiently high mechanical strength, such may beused along without other substances. The substance having a functionalgroup may be also used in the form of mixture with other high molecularcompound having no functional group so as to adjust the properties(e.g., mechanical strength, refractive index, dielectric constant) ofthe final matrix.

The functional reaction as mention above refers to a reaction ofreducing or eliminating the interaction between the functional group ofthe matrix-forming substance and the metal, semiconductor or precursorthereof to accelerate precipitation of metal or semiconductor in theform of fine grains. Any functional groups may be used as long as theyexhibit an interaction with the metal, semiconductor or precursorthereof to accelerate dissolution, in other words, to increase its dopedamount before the functional reaction, and they do not inhibit (rather,accelerate) precipitation of the fine grains after the functionalreaction. The functional group is exemplified with a carboxyl group, anamino group, an amido group, and a hydroxyl group, and examples of thefunctional group include intramolecular reactions or intermolecularreactions resulting on structural changes, such as cyclization,condensation, addition reaction, elimination reaction, and the like.These reactors are initiated by heat, chemical agents such as catalysts,light, or the like. Typical examples of the functional reaction are (1)imide ring formation reaction by heat treatment or chemical treatment,(2) reaction of a functional group such as a carboxyl group, an aminogroup, a hydroxyl group and a carboxylic anhydride with an isocyanategroup or an epoxy group, (3) acid addition salt formation reaction byacid treatment of an amino compound, and (4) others.

The first embodiment of the nonlinear optical element according to thepresent invention is characterized in that finely divided grains of asemiconductor or metal are dispersed in a high molecular compound formedby thermosetting or chemical treatment, particularly a high molecularcompound containing a repeating structural unit represented by thefollowing general formula (1) or a compound containing the highmolecular compound: ##STR1## wherein X represents a tetravalent organicgroup having not less than 2 carbon atoms; and Y represents a divalentorganic group having not less than 2 carbon atoms.

The second embodiment of the nonlinear optical element according to thepresent invention is characterized in that finely divided grains of asemiconductor or metal are dispersed in a high molecular compoundcontaining an imide structure represented by any one of the followinggeneral formulae (2) to (4) in its side chain or crosslinked moiety or amatrix containing the high molecular compound: ##STR2## wherein x and Yare as defined above; W represents an organic group having not less than2 carbon atoms necessary for the formation of an imide ring; and Zrepresents an alkyl, aryl or aralkyl group.

The third embodiment of the nonlinear optical element according to thepresent invention is prepared by a process which comprisesincorporating, in a matrix containing a high molecular compound havingat least one functional group which interacts with a metal orsemiconductor or its starting material to accelerate dissolution of themetal or semiconductor or its starting material (hereafter"interaction-exhibiting high molecular compound), (i) the metal orsemiconductor or its starting material and (ii) a compound which reactswith said functional group to reduce or eliminate its interaction withsaid metal or semiconductor or its starting material (hereafter"interaction-eliminating compound"), and then subjecting the material toheat treatment. In some detail, finely divided grains of a semiconductoror metal are dispersed in a matrix formed by reacting a high molecularcompound containing a functional group such as a carboxyl group, anamino group, a hydroxyl group and carboxylic anhydride with a compoundcontaining an epoxy group or an isocyanate group, etc.

The fourth embodiment of the nonlinear optical element according to thepresent invention is characterized in that finely divided grains of asemiconductor or metal are dispersed in an organic compound whosechemical structure has been changed by heat treatment or chemicaltreatment, particularly a mixture of a compound represented by thefollowing general formula (5) and a high molecular compound as a matrix:##STR3## wherein W is as defined above; and U represents an monovalentorganic group which may be substituted by an imide ring.

The fifth embodiment of the nonlinear optical element according to thepresent invention is characterized in that the matrix is an acid salt ofan ammonium salt-containing high molecular compound, preferably anamino-containing high molecular compound consisting of repeatingstructural units represented by the following general formula (6) or asubstance containing the high molecular compound, in which finelydivided grains of a semiconductor or metal are dispersed: ##STR4##

The sixth embodiment of the nonlinear optical element according to thepresent invention is characterized in that the matrix is a highmolecular compound consisting of repeating structural units representedby the following general formula (7) or a substance containing the highmolecular compound, in which finely divided grains of a semiconductor ormetal are dispersed: ##STR5##

The seventh embodiment of the nonlinear optical element according to thepresent invention is characterized in that the matrix is a mixture of ahigh molecular compound and a hydrolyzate of a compound comprising ahydrolyzable substituent bonded to a trivalent atom or a tetravalentatom other than carbon, said high molecular compound being selected fromthe group consisting of a high molecular compound having a repeatingunit represented by formula (1); a high molecular compound having animido structure of formula (2), (3) or (4) at its side chain orcrosslinked moiety; a compound obtained by the reaction of a highmolecular compound having a carboxyl group, an amino group or a hydroxylgroup and a compound having an epoxy group or an isocyanate group; anorganic compound represented by formula (5); an amino group-containinghigh molecular compound have a repeating unit represented by formula(6); and a high molecular compound having a repeating unit representedby formula (7), in which matrix finely divided grains of a semiconductoror metal are dispersed: ##STR6## wherein X represents a tetravalentorganic group having not less than 2 carbon atoms; Y represents adivalent organic group having not less than 2 carbon atoms; W representsan organic group having not less than 2 carbon atoms necessary for theformation of an imide ring; Z represents an alkyl, aryl or aralkylgroup; and U represents a monovalent organic group which may contain asubstituent capable of forming an imide ring.

The eighth embodiment of the nonlinear optical element according to thepresent invention is characterized in that the matrix is a hydrolyzateof a compound having a hydrolyzable substituent bonded to a trivalentatom or a tetravalent atom other than carbon atom, preferably ahydrolyzate of a silane compound represented by the following generalformula (8) or (8A), in which matrix finely divided grains of asemiconductor or a metal are dispersed: ##STR7## wherein X¹ and X² eachrepresent a divalent organic group having not less than 2 carbon atoms;and the plurality of Y¹ 's may be the same or different and eachrepresent a hydrolyzable functional group. ##STR8## wherein X^(1A)represents tetravalent organic residue having not less than two carbonatoms; the plurality of X² may be the same or different and eachrepresents a divalent organic residue having not less than two carbonatoms; the plurality of Y¹ may be the same or different and eachrepresents a hydrolyzable functional group; Y² represents a monovalentor divalent non-hydrolyzable organic group; n is an integer of 1 to 3;and m is 0, 1, or 2.

The ninth embodiment of the nonlinear optical element according to thepresent invention is characterized in that the matrix is a hydrolyzateof a polyamide compound containing in its main chain or side chain asilyl group having one or more hydrolyzable substituents or a mediumconsisting of the polyamide compound and a hydrolyzate of a compoundhaving a hydrolyzable substituent bonded to a trivalent atom ortetravalent atom, in which matrix finely divided grains of asemiconductor or metal are dispersed.

The first embodiment of the nonlinear optical element according to thepresent invention can be prepared by a process which comprisessubjecting a thermosetting material, particularly a high molecularcompound having repeating structural units represented by the followinggeneral formula (9), as a functional group-containing matrix-formingsubstance to heat treatment or chemical treatment so that finely dividedgrains of a semiconductor or metal are separated out: ##STR9## wherein Xrepresents a tetravalent organic group having not less than 2 carbonatoms; and Y represents a divalent organic group having not less than 2carbon atoms.

The second embodiment of the nonlinear optical element according to thepresent invention can be prepared by a process which comprises the useof at least one high molecular compound having in its side chain orcrosslinked moiety an amide acid structure represented by any one of thefollowing general formulae (10) to (12) as a functional group-containingmatrix-forming substance: ##STR10## wherein X and Y are as definedabove; W represents an organic group having not less than 2 carbon atomsnecessary for the formation of an imide ring; and Z represents an alkyl,aryl or aralkyl group.

The third embodiment of the nonlinear optical element according to thepresent invention can be prepared by a process which comprisesdissolving in a solution of a interaction-exhibiting high molecularcompound with an interaction-eliminating compound, removing the solventtherefrom, and then subjecting the material to heat treatment. In somedetail, it can be prepared by the use of a mixture of a high molecularcompound containing a functional group such as a carboxyl group, anamino group, a hydroxyl group and a carboxylic anhydride and a compoundhaving an epoxy group or an isocyanate group as a functionalgroup-containing matrix-forming substance.

The fourth embodiment of the nonlinear optical element according to thepresent invention can be prepared by a process which comprises the useof a mixture of a compound represented by the following general formula(13) and a high molecular compound as a functional group-containingmatrix-forming substance: ##STR11## wherein W is as defined above; andU¹ represents an organic group which may contain a substituent capableof forming an imide ring.

The fifth embodiment of the nonlinear optical element according to thepresent invention can be prepared by a process which comprises the useof an amino-containing high molecular compound, preferably anamino-containing high molecular compound containing repeating structuralunits represented by the following general formula (14), as afunctional-containing matrix-forming substance: ##STR12##

The sixth embodiment of the nonlinear optical element according to thepresent invention can be prepared by a process which comprises the useof a high molecular compound containing repeating structural unitsrepresented by the following general formula (15) as a functionalgroup-containing matrix-forming substance: ##STR13## wherein Rrepresents an alkyl group.

The seventh embodiment of the nonlinear optical element according to thepresent invention can be prepared by a process which comprises the useof a mixture of a high molecular compound consisting of repeatingstructural units represented by the foregoing general formula (9) and ahydrolyzate of a compound having a hydrolyzable substituent bonded to atrivalent atom or a tetravalent atom other than a carbon atom as afunctional group-containing matrix-forming substance.

The eighth embodiment of the nonlinear optical element according to thepresent invention can be prepared by a process which comprises the useof a silane compound represented by the foregoing general formula (8) or(8A) as a functional group-containing matrix-forming substance.

The ninth embodiment of the nonlinear optical element according to thepresent invention can be prepared by a process which comprises the useof a polyamic acid compound containing in its main chain or side chain asilyl group having at least one hydrolyzable substituent as a functionalgroup-containing matrix-forming substance.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example and to make the description more clear, reference ismade to the accompanying drawings in which:

FIGS. 1(a) and 1(b) shows an infrared absorption spectrum of compositefilms of Examples 1, 2 and 5 before and after treatment, respectively;

FIG. 2 shows an X-ray diffraction spectrum of a high molecularcompound/CuCl composite film of Example 7 (determined with CuKα rays);

FIG. 3 shows an absorption spectrum of a high molecular compound/CuClcomposite film of Example 7;

FIG. 4 shows an X-ray diffraction spectrum of a high molecularcompound/CuBr composite film of Example 8 (determined with CuKα rays);

FIG. 5 shows an absorption spectrum of a high molecular compound/CuBrcomposite film of Example 8;

FIG. 6 shows an absorption spectrum of a high molecular compound/CuClcomposite film of Example 11;

FIGS. 7(a) and 7(b) shows an infrared absorption spectrum of Example 34wherein FIG. 7(a) shows the result obtained after coated and dried andFIG. 7(b) shows the result after heat treatment at 200° C. for 1 hour;

FIG. 8 shows an X-ray diffraction pattern of a high molecularcompound/CuCl composite film of Example 34;

FIG. 9 illustrates an apparatus for evaluating nonlinear opticalcharacteristic of the thin films prepared in the Examples.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be further described hereinafter.

In every embodiment of the present invention as described above, thematrix contains fine grains of metal or semiconductor generally in anamount of 0.01 to 99.0% by weight, preferably 0.1 to 99.0% by weight andparticularly 10.0 to 95.0% by weight, based on the total weight of thenon-linear optical element. The matrix substance may also containanother matrix substance, preferably not more than 50% by weight,preferably not more than 30% by weight.

In the present invention, the imide ring formation reaction (1)corresponds to the formation of the foregoing first, second, fourth,seventh, eighth and ninth embodiments of the nonlinear optical element.The reaction (2) corresponds to the formation of the third embodiment ofthe nonlinear optical element. The acid addition seat formation reaction(3) corresponds to the formation of the fifth embodiment of thenonlinear optical element. The hydrolysis reaction (4) corresponds tothe formation of the sixth embodiment of the nonlinear optical element.

In the present invention, the first embodiment of the nonlinear opticalelement preferably comprises a high molecular compound having repeatingstructural units represented by the foregoing general formula (1) whichcan be prepared from a high molecular compound having repeatingstructural units represented by the foregoing general formula (9). Anyother high molecular compounds can be similarly used so far as they arethermosetting. In other words, any high molecular compounds which in theform of precursor can thoroughly make a solid solution of asemiconductor or metal or its starting material, which undergothermosetting reaction to change its chemical properties, or which arethoroughly transparent to the wavelength of light used, i.e., thewavelength at which finely divided grains of a semiconductor or metalexhibit a great nonlinear optical effect can be used.

X has one or two benzene nuclei which may be substituted. When X has twobenzene nuclei, the two benzene nuclei connect directly or connect viaan alkylene group having 1 to 10 carbon atoms which may be substitutedby an oxygen atom, a carbonyl group or a halogen atom. X preferably hasan unsubstituted benzene nucleus. X has 2 to 30 carbon atoms, preferably6 to 20 carbon atoms.

Y has an aromatic group which may be substituted by one or twosubstituents. When Y has two benzene nuclei, the two benzene nucleiconnect directly or connect via an alkylene group having 1 to 10 carbonatoms which may be substituted by an oxygen atom, a sulfur atom or ahalogen atom. Examples of a substituent of the benzene nuclei include analkyl group having 1 to 5 carbon atoms which may be substituted by ahalogen atom, an alkoxy group having 1 to 5 carbon atoms or a halogenatom. Y has 2 to 30 carbon atoms, preferably 6 to 20 carbon atoms.

Referring further to the high molecular compound having repeatingstructural units represented by the general formula (9) used as aprecursor of such a high molecular compound, examples of X in thegeneral formula (9) include organic residues represented by thefollowing structural formulae: ##STR14## wherein k represents an integer1 to 6.

Examples of Y include organic residues represented by the followingstructural formulae: ##STR15## wherein a represents an integer 1 to1,000.

These exemplary high molecular compounds can be synthesized from atetracarboxylic dihydrate having a chemical structure represented by Xand a diamine having a structure represented by Y. These high molecularcompounds are soluble in a polar organic solvent such asdimethylformamide, dimethylacetamide, n-methylpyrrolidone, dimethylsulfoxide, dimethyl sulfonamide, m-cresol, p-chlorophenol,dimethylimidazoline, tetramethylurea, diglyme, triglyme and tetraglyme.Thus, these high molecular compounds can be easily formed into a film byspin coating or dip coating process or worked into a fiber. Theintrinsic viscosity η! of these high molecular compounds is preferablyin the range of 0.1 to 6 dl/g at a temperature of 30° C. in a solventsuch as dimethylacetamide. The intrinsic viscosity as defined herein isdetermined by extrapolating the relative viscosity or reduced viscosityat various concentrations calculated from measurements of the relativeviscosity at various polymer concentrations to the concentration of 0.Further, these high molecular compounds contain many amide acidstructures as functional groups to interact with various inorganicelements and inorganic compounds. Thus, these high molecular compounds,in the form of solution or solid free of solvent, can comprise a metalor semiconductor or a compound as its starting material stably dissolvedtherein in a relatively high concentration. When heated or subjected tochemical treatment after dipped in a mixture of acetic anhydride andpyridine (about 1:1), these high molecular compounds undergo thefollowing reaction.

The heat treatment can be effected at a temperature of 100° to 400° C.,preferably 150° to 300° C., for example, as relatively low as around200° C., and for 1 minute to 5 hours, preferably 5 minutes to 3 hours.Examples of solvents which can be used besides the foregoing solventsinclude a mixture of acetic anhydride, pyridine and benzene and amixture of acetic anhydride, pyridine and dimethylacetamide. The solventtreatment is conducted by stirring in a solvent.

The foregoing dissolution, heating and chemical treatment are allpreferably effected in vacuo or in an inert atmosphere. ##STR16##wherein n represents a polymerization degree.

When the foregoing reaction occurs, the elimination of the amide acidstructure contained in the high molecular compound which is a matrix isfollowed by the formation of an imide ring structure with the depositionof the metal or semiconductor or the compound as its starting materialwhich has been dissolved as a dopant in the high molecular compound.Other high molecular compound may be also used so as to adjust thephysical properties (e.g., mechanical strength, refractive index,dielectric constant) of the final matrix.

In the second embodiment of the nonlinear optical element according tothe present invention, the matrix consists of or comprises a highmolecular compound having its side chain or crosslinked moiety an imidestructure represented by any one of the foregoing general formulae (2)to (4). This high molecular compound can be prepared by a process whichcomprises dissolving a semiconductor or metal or its starting materialin a solution of at least one high molecular compound having in its sidechain or crosslinked moiety an amide acid structure represented by anyone of the foregoing general formulae (10) to (12) or a mixture thereofwith other high molecular compounds, removing the solvent therefrom, andthen subjecting the material to heat treatment or chemical treatment.The amount of the above other high molecular compounds is 50 wt % orless, preferably 30 wt % or less based on the total amount of thematrix.

In the foregoing general formulae (2) to (4) and (10) to (12), Wrepresents an organic group having not less than 2 carbon atomsnecessary for the formation of an imide ring. Specific examples of suchan organic group include the following groups: ##STR17##

Z represents an alkyl group having 1 to 5 carbon atoms, aryl grouphaving 6 to 20 carbon atoms or aralkyl group having 7 to 20 carbonatoms. Specific examples of Z include a methyl group, an ethyl group, abenzyl group, a p-methylphenyl group, and a p-methoxyphenyl group.

The at least one high molecular compound having in its side chain orcrosslinked moiety an amide acid structure represented by any one of theforegoing general formulae (10) to (12) to be used in the presentinvention is not specifically limited but is preferably one whichthoroughly makes a solid solution of a metal or semiconductor or itsstarting material, which undergoes heat treatment or chemical treatmentto change its chemical properties or which exhibits a sufficiently smallabsorption at the wavelength of light used, i.e., the wavelength atwhich finely divided grains of a semiconductor exhibits a greatnonlinear optical effect.

As such a high molecular compound there may be used one having an imidestructure which has been derived from a high molecular compound havingan imide precursor structure as described below by heat treatment orchemical treatment. In other words, the main chain structure of the highmolecular compound having its side chain or crosslinked moiety an imideprecursor structure is not specifically limited. Examples of such a mainchain structure include polyethylene resin, polystyrene resin,polyacrylate resin, polymethacrylate resin, polycarbonate resin,polyester resin, cellulose resin, silicone resin, vinyl polymer,polyamide resin, polyamide-imide resin, polyurethane resin, polyurearesin, and copolymers thereof. The desired high molecular compound isselected from the group consisting of high molecular compounds havingsuch a main chain structure and having in its side chain or crosslinkedmoiety at least one imide precursor structure. The desired highmolecular compound may have a polymer structure formed with a highmolecular compound having the same main chain structure as mentionedabove free of imide precursor structure. Such a high molecular compoundmay be used in the form of mixture of two or more such high molecularcompounds or in admixture with a high molecular compound having the samemain chain structure as mentioned above free of imide precursorstructure depending on the purpose of controlling the physicalproperties (e.g., mechanical strength, refractive index, dielectricconstant) so far as its optical transparency is not lowered by phaseseparation. Examples of the imide precursor structure contained in theside chain or crosslinked moiety in the high molecular compound includea carboxyl group, an amino group, and an amide acid group, which areconverted to an imide structure when subjected to heat treatment orchemical treatment. An imide precursor structure having an amide acidstructure which can be easily changed to an imide structure even in asolid phase is desirable. This amide acid can be obtained by reacting ahigh molecular compound having in its side chain or crosslinked moietyan amino group with a dicarboxylic anhydride or tetracarboxylicdianhydride or reacting a high molecular compound having in its sidechain or crosslinked moiety an acid anhydride structure with an amine ordiamine. Alternatively, the similar reaction may be effected at thestage of monomer to synthesize a monomer having an amide acid structurewhich is then allowed to undergo polymerization reaction to obtain ahigh molecular compound having in its side chain or crosslinked moietyan imide precursor structure.

These high molecular compounds are soluble in a polar organic solventsuch as dimethylformamide, dimethylacetamide, n-methylpyrrolidone,dimethyl sulfoxide, dimethyl sulfonamide, m-cresol, p-chlorophenol,dimethylimidazolidone, tetramethylurea, diglyme, triglyme andtetraglyme. Thus, these high molecular compounds can be easily formedinto a film by spin coating or dip coating process or worked into afiber. The intrinsic viscosity η! of these high molecular compounds ispreferably in the range of 0.1 to 6 dl/g at a temperature of 30° C. in asolvent such as a dimethylacetamide. Further, these high molecularcompounds contain amide acid structures as functional groups to interactwith various inorganic elements and inorganic compounds. Thus, thesehigh molecular compounds, in the form of solution or solid free ofsolvent, can comprise a metal or semiconductor or a compound as itsstarting material stably dissolved therein in a relatively highconcentration. When heated or subjected to chemical treatment with amixture of acetic anhydride and pyridine, these high molecular compoundsundergo dehydration and ring closure to become high molecular compoundshaving an imide structure represented by any one of the foregoinggeneral formulae (2) to (4). The heat treatment is effected at atemperature not higher than the decomposition temperature of these highmolecular compounds.

When the foregoing reaction occurs, the amide acid structure containedin the high molecular compound which is a matrix is eliminated with thesubsequent formation of an imide ring structure as well as thedeposition of the metal or semiconductor or the compound as its startingmaterial which has been dissolved as a dopant in the high molecularcompound.

In the third embodiment of the nonlinear optical element according tothe present invention, the matrix is formed by subjecting a mixture of ahigh molecular compound containing a functional group such as a carboxylgroup, an amino group, a hydroxyl group or a carboxylic anhydride and acompound containing a group such as an epoxy group and an isocyanategroup to heat treatment or other treatment. In some detail, the matrixis prepared by a process which comprises dissolving in a solution of aninteraction-exhibiting high molecular compound with aninteraction-eliminating compound, removing the solvent therefrom, andthen subjecting the material to heat treatment or other treatment. Moreparticularly, the matrix is preferably prepared by a process whichcomprises dissolving in a solution of an interaction-exhibiting highmolecular compound with an interaction-eliminating compound (firststep), forming the solution by coating or other methods, removing thesolvent therefrom to obtain a solid solution (second step), and thensubjecting the solid solution to heat treatment (third step) to preparea desired composite material having microcrystals of a semiconductor ormetal separated out therein. The matrix can also be produced bydissolving a metal or semiconductor or its starting material in asolution of the interaction-exhibiting high molecular compound, removingthe solvent, dispersing the interaction-eliminating compound, in theresulting medium and then heating the medium. The composite material maybe optionally subjected to reduction with hydrogen or chemical treatmentwith a sulfide such as hydrogen sulfide.

The high molecular compound having a carboxyl group, an amino group, ahydroxy group or a carboxylic anhydride group reacts with an equivalentamount of another high molecular compound having an isocyanate group oran epoxy group. These high molecular compounds are charged in a reactorin the ratio of the former to the latter of from 10/1 to 1/3, preferably4/1 to 1/2, and more preferably from 4/1 to 1/1.

The interaction-exhibiting high molecular compound to be used in thepresent invention is not specifically limited but is preferably onewhich thoroughly makes a solid solution of a metal or semiconductor orits starting material, which can easily undergo heat reaction with aninteraction-eliminating compound or which exhibits a sufficiently smallabsorption at the wavelength of light used, i.e., the wavelength atwhich finely divided grains of a semiconductor exhibits a greatnonlinear optical effect.

As such an interaction-exhibiting high molecular compound there may beused one set forth below. In other words, the main chain structure ofthe high molecular compound is not specifically limited so far as it hasa reactive functional group such as a carboxyl group, an amino group,hydroxyl group and carboxylic anhydride in its side chain or crosslinkedmoiety. Examples of such a main chain structure include polyethyleneresin, polystyrene resin, polyacrylate resin, polymethacrylate resin,polycarbonate resin, polyester resin, cellulose resin, silicone resin,vinyl polymer, polyamide resin, polyamide-imide resin, polyurethaneresin, polyurea resin, and copolymers thereof. Theinteraction-exhibiting high molecular compound may have a copolymerstructure formed with a high molecular compound having the same mainchain structure as mentioned above free of reactive functional groupsuch as a carboxyl group, an amino group, a hydroxyl group andcarboxylic anhydride. Such a high molecular compound may be used in theform of mixture of two or more such high molecular compounds or inadmixture with a high molecular compound having the same main chainstructure as mentioned above free of reactive functional group such as acarboxyl group, an amino group, hydroxyl group and carboxylic anhydridedepending on the purpose of controlling the physical properties (e.g.,mechanical strength, refractive index, dielectric constant) so far asits optical transparency is not lowered by phase separation.

The interaction-eliminating compound is not specifically limited.Examples of such an interaction-eliminating compound includepolyisocyanates such as monoisocyanate and diisocyanate and polyepoxidecompounds such as monoepoxide and diepoxide, which can react with thefunctional group. Two or more these compounds may be used incombination. Alternatively, compounds having these reactive groupsbonded to high molecular compounds may be used.

If a polyisocyanate such as diisocyanate or polyepoxide such asdiepoxide is used, it serves as a crosslinking agent for high molecularcompound to improve the solvent resistance thereof. Taking into accountflexibility or the like, it may be used in admixture with a monoepoxideor in combination with a monoisocyanate. These compounds are notspecifically limited so far as they can react with the foregoingfunctional group. Examples of these compounds will be set forth below.

Examples of these compounds include isocyanates such asmethylisocyanate, ethylisocyanate, chloroethylisocyanate,propylisocyanate, butylisocyanate, cyclohexylisocyanate,phenylisocyanate, methylphenylisocyanate, methoxyphenylisocyanate,chlorophenylisocyanate, nitrophenylisocyanate, carboethoxyisocyanate,toluenesulfonylisocyanate and biphenylisocyanate, polyisocyanates suchas hexamethylene-1,6-diisocyanate, diphenylmethanediisocyanate,toluenediisocyanate, naphthalene-1,5-diisocyanate andbenzene-1,3,5-triisocyanate, monoepoxides such as 1,2-epoxycyclohexane,1,2-epoxy-3-phenylpropane, 3,4-epoxy-2,2,5,5-tetramethyl-3-phenylhexaneand phenolglycidylether, polyepoxides such as2',3,2',3'-diepoxydicyclopentylether, bisphenol A-diglycidylether,bisphenol C-diglycidylether, bisphenol Z-diglycidylether,glycerintriglycidylether, triglycidyl-p-aminophenol,trihydroxybiphenyltriglycidylether and bisresorcinoltetraglycidylether,and high molecular compounds having the foregoing reactive groups in themain chain or side chain in polyethylene resin, polystyrene resin,polyacrylate resin, polymethacrylate resin, polycarbonate resin,polyester resin, cellulose resin, silicone resin, vinyl resin, polyamideresin, polyamide-imide resin, polyurethane resin or polyurea resin.

The interaction-exhibiting high molecular compound, optionally inadmixture with a high molecular compound free of the functional group,and-the interaction-eliminating compound may be dissolved in a polarsolvent such as dimethylformamide, dimethylacetamide,n-methylpyrrolidone, dimethylsulfoxide, dimethylsulfonamide, m-cresol,p-chlorophenol, dimethylimidazolidone, tetramethylurea, diglyme,triglyme, tetraglyme and sulforan as well as a halogenated solvent suchas methylene chloride and chloroform, an alcohol such as methanol,ethanol, butanol and terpineol, a ketone such as acetone and methylethyl ketone, an ester such as ethyl acetate and butyl acetate, an ethersuch as diethyl ether and dibutyl ether or a hydrocarbon solvent such astoluene, xylene and tridecane, mixed with a metal or semiconductor orits starting material as mentioned later, and then subjected to coatingprocess such as spin coating and dip coating to make a film or subjectedto other forming processes to make a form. The material can also beworked into a fiber. The foregoing interaction-exhibiting high molecularcompound preferably exhibits an intrinsic viscosity η! of 0.1 to 6 dl/gin a solvent such as a dimethylacetamide at a temperature of 30° C.

The foregoing functional group-containing interaction-exhibiting highmolecular compound interacts with various inorganic elements andinorganic compounds to form a complex or salt to accelerate thedissolution of the inorganic elements and inorganic compounds. Thus,these high molecular compounds, in the form of solution or solidsolution free of solvent, can comprise a metal or semiconductor or itsstarting material dissolved stably therein in a relatively highconcentration. The solid solution thus obtained may be then heated toreact the functional group in the interaction-exhibiting high molecularcompound with the interaction-eliminating compound such as isocyanate toobtain a high molecular composite material having a metal orsemiconductor dispersed therein. The heat treatment is effected at atemperature of not higher than the decomposition temperature of the highmolecular compound, preferably not higher than 150° C., though dependingon the reactivity of the functional group-containing high molecularcompound and the compound such as isocyanate.

When the foregoing reaction occurs, the functional groups contained inthe interaction-exhibiting high molecular compound partially or entirelyundergo reaction to reduce or eliminate its interaction with a metal orsemiconductor or its starting material, allowing the metal orsemiconductor or its starting which has interacted with the functionalgroups as a dopant to be separated out.

In the fourth embodiment of the nonlinear optical element according tothe present invention, the matrix comprises a compound represented bythe foregoing general formula (5) and a high molecular compound. Thematrix is formed as follows. The preparation process comprisesdissolving in a solution of a high molecular compound in a propersolvent (which is the same as the polar solvent in the above thirdembodiment) a mixture of a metal or semiconductor or its startingmaterial and an organic compound represented by the foregoing generalformula (13) which interacts with the metal or semiconductor or itsstarting material and undergoes heat treatment or chemical treatment tochange its chemical structure (first step), removing the solventtherefrom to obtain a solid solution of the high molecular compound,organic compound and semiconductor or its starting material (secondstep), and then subjecting the material to heat treatment or chemicaltreatment to change the chemical structure of the organic compound toallow the desired microcrystals of semiconductor or metal to beseparated out (third step).

In formula (5), U is preferably an alkyl group having 1 to 5 carbonatoms or an alkoxyl group having 1 to 5 carbon atoms, which may furtherbe substituted by the compound having an imide structure represented byformulae (2), (3) or (4).

The high molecular compound as a constituent component of the matrix inthis embodiment is not specifically limited but is preferably one whichis thoroughly transparent at the wavelength of light used, i.e., thewavelength at which finely divided grains of a semiconductor exert agreat nonlinear optical effect. Examples of such a high molecularcompound include polyethylene resin, polystyrene resin, polyacrylateresin, polymethacrylate resin, polycarbonate resin, polyester resin,cellulose resin, silicone resin, vinyl resin, polyamide resin, polyimideresin, polyamide-imide resin, polyurea resin, polyurethane resin, andhigh molecular compounds having a copolymer structure formed therewith.A plurality of these high molecular compounds may be used in admixturedepending on the purpose of controlling the physical properties (e.g.,refrax index, mechanical strength, dielectric constant) so far phaseseparation or the like doesn't lower the optical transparency thereof.

The organic compound is used in an amount of 70 wt % or less, preferably50 wt % or less, based on the total amount of the matrix.

The organic compound which is used in admixture with the foregoing highmolecular compound and undergoes heat treatment or chemical treatment tochange its chemical structure is not specifically limited but ispreferably one which interacts with the foregoing metal or semiconductoror its starting material to accelerate the dissolution of the foregoingmetal or semiconductor or its starting material and receives an externalstimulation to change its chemical structure to reduce or eliminate itsinteraction with the metal or semiconductor or its starting material. Anexample of such an organic compound is a compound synthesized from anamine represented by the foregoing general formula (5) and an acidanhydride. Such a compound has an amide acid structure and thusinteracts with a metal or semiconductor or its starting material toaccelerate the dissolution thereof. When such a compound is subjected toheat treatment or other treatments such as dipping in a mixture ofacetic anhydride and pyridine, it undergoes the following reaction:##STR18##

The heat treatment can be effected at a temperature of 100° to 400° C.,preferably 150° to 300° C., and for 1 minute to 5 hours, preferably 5minutes to 3 hours. The solvent treatment is conducted by stirring in asolvent which is enough to stir.

When this reaction occurs, the amide structure is eliminated, followedby the formation of an imide ring structure with the deposition of themetal or semiconductor or its starting material which has been dissolvedinteracted in this compound as a dopant.

Alternatively, a chelating agent capable of forming a complex compoundwith a metal or semiconductor or its starting material, such asacetylacetone and ethylenediamine, may be used to form a complexcompound which is then subjected to heating so that finely dividedgrains of a metal or semiconductor or its starting material may besimilarly separated out.

The fifth embodiment of the nonlinear optical element according to thepresent invention is characterized in that finely divided grains of asemiconductor or metal are dispersed in a matrix containing at least anacid salt of an amino-containing high molecular compound. Thisembodiment of the nonlinear optical element can be formed by a processwhich comprises dissolving a semiconductor or metal or its startingmaterial in a solution containing at least an amino-containing highmolecular compound, obtaining a solid solution and then treating thematerial with an acid to allow finely divided grains of a semiconductoror metal to be separated out.

In other words, the present invention provides a process which comprisesmixing a solution of a high molecular compound in a proper solvent witha metal or semiconductor or its starting to make a solution (firststep), removing the solvent after molding by means of coating or otherprocess in vacuo to obtain a solid solution of the high molecularcompound and the semiconductor or its starting material (second step),and then treating the solid solution with an acid to change the highmolecular compound as a matrix to allow the desired semiconductor ormetal microcrystals to be separated out (third step).

The high molecular compound to be used in the present invention is notspecifically limited but is preferably one which in the form ofprecursor can thoroughly make a solid solution of a semiconductor or itsstarting material, which undergoes acid treatment to change its chemicalproperties or which is thoroughly transparent at the wavelength of lightused, i.e., the wavelength at which finely divided grains of asemiconductor exert a great nonlinear optical effect. Examples of such ahigh molecular compound include the following compounds: ##STR19##wherein p represents a polymerization degree, and the high molecularcompound exhibits an intrinsic viscosity η! of 0.1 to 6 dl/g.

These exemplary high molecular compounds are soluble in water or a polarorganic solvent such as dimethylformamide, dimethylacetamide,n-methylpyrrolidone, dimethyl sulfoxide, dimethyl sulfonamide, m-cresol,p-chlorophenol, dimethylimidazolidone, tetramethylurea, diglyme,triglyme and tetraglyme. Thus, these high molecular compounds can beeasily formed into a film by spin coating or dip coating process orworked into a fiber. Further, these high molecular compounds containmany amine structures as functional groups to interact with variousinorganic elements and inorganic compounds. Thus, these high molecularcompounds, in the form of solution or solid solution free of solvent,can comprise a metal or semiconductor or a compound as its startingmaterial stably dissolved therein in a relatively high concentration.When subjected to chemical treatment with an acid such as hydrochloricacid, these high molecular compounds undergo the following reaction.##STR20## wherein p represents a polymerization degree.

When this reaction occurs, the amino group contained in the highmolecular compound as a matrix turns to a hydrochloride structure,causing the metal or semiconductor or compound as its starting materialwhich has been dissolved coordinated to the amino group in the highmolecular compound as a dopant to be separated out.

These high molecular compounds may be used singly or in combination, orin admixture with a proper amount of high molecular compounds free ofamino group for the purpose of controlling the physical properties(e.g., mechanical strength, dielectric constant, refrax index). Further,a copolymer high molecular compound consisting of an amino-containingmoiety and an amino-free moiety may be used as well.

The acid to be used in the acid treatment is not specifically limited tohydrochloric acid but may be an acid capable of forming a salt with anamino group, such as acetic acid.

The sixth embodiment of the nonlinear optical element according to thepresent invention is characterized in that finely divided grains of asemiconductor or metal are dispersed in a matrix containing at least ahigh molecular compound consisting of repeating structure unitsrepresented by the foregoing general formula (7). This embodiment of thenonlinear optical element can be formed by a process which comprisesdissolving a semiconductor or metal or its starting material in asolution containing at least a high molecular compound consisting ofrepeating structure units represented by the foregoing general formula(15), removing the solvent after molding by means of coating, etc., andthen subjecting the material to heat treatment to allow finely dividedgrains of a semiconductor or metal to be separated out.

In other words, the present invention provides a process which comprisesmixing a solution of a high molecular compound consisting of repeatingstructure units represented by the foregoing general formula (15) in aproper solvent with a metal or semiconductor or its starting material tomake a solution (first step), removing the solvent after molding bymeans of coating, etc. to obtain a solid solution of the high molecularcompound and the semiconductor or its starting material (second step),and then subjecting the solid solution to heat treatment to change thehigh molecular compound as a matrix to allow the desired semiconductoror metal microcrystals to be separated out (third step).

The high molecular compound consisting of repeating structure unitsrepresented by the foregoing general formula (15) is soluble in water ora polar organic solvent such as dimethylformamide, dimethylacetamide,n-methylpyrrolidone, dimethyl sulfoxide, dimethyl sulfonamide, m-cresol,p-chlorophenol, dimethylimidazolidone, tetramethylurea, diglyme,triglyme and tetraglyme. Thus, the high molecular compound can be easilyformed into a film by spin coating or dip coating process or worked intoa fiber. Further, the high molecular compound contains many aminestructures as functional groups to interact with various inorganicelements and inorganic compounds. Thus, the high molecular compound, inthe form of solution or solid free of solvent, can comprise a metal orsemiconductor or a compound as its starting material stably dissolvedtherein in a relatively high concentration. When subjected to heattreatment, the high molecular compound undergoes the following chemicalchange: ##STR21## wherein R represents an alkyl group having 1 to 10carbon atoms, preferably 1 to 5 carbon atoms; r represents apolymerization degree; and the high molecular compound exhibits anintrinsic viscosity η! of 0.1 to 6 dl/g.

The heat treatment can be effected at a temperature of 30° to 400° C.,preferably 70° to 300° C., and for 1 minute to 5 hours, preferably 5minutes to 3 hours.

When this reaction occurs, the amino group contained in the highmolecular compound as a matrix is eliminated, allowing the metal orsemiconductor or a compound as its starting material which has beendissolved coordinated to the amino group in the high molecular compoundto be separated out.

In the seventh embodiment of the nonlinear optical element according tothe present invention, finely divided grains of a semiconductor or-metalwhich exert a nonlinear optical effect are contained in a mediumconsisting of a hydrolyzate of a compound having a hydrolyzablesubstituent bonded to a trivalent atom or a tetravalent atom other thancarbon and a high molecular compound having repeating structure unitsrepresented by the foregoing general formula (1).

This nonlinear optical element can be prepared by carrying out thefollowing successive procedure to allow finely divided grains of asemiconductor or metal to be separated out:

(a) step of dissolving finely divided grains of a semiconductor or metalwhich exert a nonlinear optical effect or a metal salt or metal complexas its starting material and a high molecular compound having repeatingstructure units represented by the foregoing general formula (1) in thepresence of a proper solvent;

(b) step of mixing the solution thus obtained with a compound having ahydrolyzable substituent bonded to a trivalent atom or a tetravalentatom other than carbon atom or a hydrolyzate thereof to make a uniformsolution;

(c) step of allowing the hydrolyzable compound thus obtained to undergohydrolysis to gelatinize the solution; and

(d) step of removing the solvent therefrom, and then subjecting thematerial to heat treatment to allow finely divided grains of asemiconductor or metal to be separated out.

The hydrolyzable compound to be used in the present invention may bepreferably used in combination with at least one selected from the groupconsisting of network-forming silane compounds represented by thefollowing general formulae (16), (17) and (18). These silane compoundsmay be used singly or in combination. ##STR22##

In these general formulae, R¹, R², R³, R⁴, R⁵ and R⁶ may be the same ordifferent and each represent a saturated or unsaturated aliphatichydrocarbon group, saturated or unsaturated alicyclic group, aromatichydrocarbon group, aralkyl group or heterocyclic- group. These organiccompound residues all may have substituents. R² and R³, or any two ofR⁴, R⁵ and R⁶ may be connected to each other to form a carbon ringresidue or heterocyclic residue. Y², Y³ and Y⁴ each represent ahydrolyzable functional group.

R¹, R², R³, R⁴, R⁵ and R⁶ are preferably an alkyl group having 1 to 20carbon atoms which may be substituted by a halogen atom or an aminogroup, or a vinyl group which may be substituted by a halogen atom.

Y² and Y⁴ are preferably an alkoxy group having 1 to 3 carbon atoms or ahalogen atom.

Specific examples of the silane compounds represented by the foregoinggeneral formulae (16), (17) and (18) include the following compounds.These compounds can be used singly or in combination.

In view of availability, formula (16) is preferably. Silane derivativesrepresented by the general formula (16):

CH₃ SiCl₃,

CH₃ Si(NCO)₃,

CH₃ Si(OCH₃)₃,

CH₃ Si(OCH₂ CH₃)₃,

CH₃ Si(O(CH₂)₂ CH₃)₃,

CH₃ Si(OCH(CH₃)₂)₃,

CH₃ Si(O)CH₂)₃ CH₃)₃,

CH₃ Si(OC(CH₃)₃)₃,

ClCH₂ Si(OCH₂ CH₃)₃,

CH₃ CH₂ SiCl₃,

CH₃ CH₂ Si(OC₃)₃,

CH₃ CH₂ Si(OCH₂ CH₃)₃,

CH₃ CH₂ Si(O(CH₂)₂ CH₃)₃,

CH₃ CH₂ Si(OCH(CH₃)₂)₃,

CH₃ CH₂ Si(O(CH₂)₃ CH₃)₃,

CH₃ CH₂ Si(OC(CH₃)₃)₃,

CH₂ ═CHSi(OCH₃)₃,

CH₂ ═CHSi(OCH₂ CH₃)₃,

CH₂ ═CHSi(OC(CH₃)₃)₃,

ClCH₂ CH₂ Si(OCH₂ CH₃)₃,

CH₃ (CH₂)₂ Si(OCH₃)₃,

Br(CH₂)Si(OCH₃)₃,

CH₂ ═CHCH₂ Si(OCH₃)₃,

CH₂ ═CHCH₂ Si(OCH₂ CH₃)₃,

Cl(CH₂)₃ Si(OCH₂ CH₃)₃,

Cl(CH₂)₃ Si(OCH₃)₃,

CH(CH₂)₃ Si(OCH₃)₃,

H₂ N (CH₂)₃ SiCl₃,

H₂ N (CH₂)₃ Si(OCH₃)₃,

H₂ N (CH₂)₃ Si (OCH₂ CH₃)₃,

NC(CH₂)₂ Si(OCH₃)₃,

NC(CH₂)₂ Si(OCH₂ CH₃)₃,

H₃ CO(CH₂)₃ Si(OCH₃)₃,

CF₃ (CH₂)₂ Si(OCH₃)₃,

CF₃ (CH₂)₂ Si(OCH₂ CH₃)₃,

CH₃ (CH₂)₄ Si(OCH₃)₃,

CH₃ (CH₂)₄ SiCl₃,

CH₃ (CH₂)₄ Si(NCO)₃,

CH₃ (CH₂)₅ Si(OCH₃)₃,

CH₃ (CH₂)₅ Si(OCH₂ CH₃)₃,

CH₃ (CH₂)₅ Si(O(CH₂)₂ CH₃)₃,

CH₃ (CH₂)₅ Si(O(CH₂)₃ CH₃)₃,

CH₃ (CH₂)₅ Si(OC(CH₃)₃)₃,

CH₃ (CH₂)₇ Si(OCH₃)₃,

CH₃ (CH₂)₇ Si(OCH₂ CH₃)₃,

Br(CH₂)₈ Si(OCH₃)₃,

CH₃ (CH₂)₉ Si(OCH₃)₃,

CH₃ (CH₂)₉ Si(OCH₂ CH₃)₃,

CH₃ (CH₂)₉ Si(OC(CH₃)₃)₃,

CH₃ (CH₂)₁₁ Si(OCH₃)₃,

CH₃ (CH₂)₁₁ Si(OCH₂ CH₃)₃,

CH₃ (CH₂)₁₁ Si(OC(CH₃)₃)₃,

CH₃ (CH₂)₁₅ Si(OCH₃)₃,

CH₃ (CH₂)₁₅ Si(OCH₂ CH₃)₃,

CH₃ (CH₂)₁₅ Si(OC(CH₃)₃)₃,

CH₃ (CH₂)₁₇ Si(OCH₃)₃,

CH₃ (CH₂)₁₇ Si(OCH₂ CH₃)₃,

CH₃ (CH₂)₁₇ Si(OCH(CH₃)₃)₃,

H₂ N (CH₂)₂ NH(CH₂)₃ Si(OCH₃)₃,

(H₃ C)₂ N(CH₂)₃ Si(OCH₃)₃,

H₂ N (CH₂)₃ OC(CH₃)₂ CH═CHSi(OCH₃)₃,

CH═CH(CH₂)₆ Si(OCH₃)₃,

H₂ N(CH₂)₁₁ Si(OCH₃)₃,

CH₃ COO(CH₂)₃ Si(OCH₃)₃,

CH═CH(CH₂)₄ Si(OCH₃)₃,

CH₂ ═CHCOO(CH₂)₃ Si(OCH₃)₃,

F₃ C(CF₂)₅ (CH₂)₂ Si(OCH₃)₃,

NCCH₂ CH₂ O--C(CH₂)₂ --CH═CHSi(OCH₃)₃,

F₃ C(CF₂)₅ (CH₂)₂ Si(OCH₂ CH₃)₃,

(CH₃ CH₂ OOC)₂ CH(CH₂)₂ Si(OCH₂ CH₃)₃, ##STR23##

Silane derivatives represented by the general formula (17):

(CH₃)₂ SiCl₂,

(CH₃)₂ Si(NCO)₂,

(CH₃)₂ Si(OCH₃)₂,

(CH₃)₂ Si(OCH₂ CH₃)₂,

(CH₃)₂ Si(O(CH₂)₂ CH₃)₂,

(CH₃)₂ Si(OCH(CH₃)₂)₂,

(CH₃)₂ Si(O(CH₂)₃ CH₃)₂,

(CH₃)₂ Si(OC(CH₃)₂,

(CH₂ CH₃)₂ Si(OCH₃)₂,

(CH₂ CH₃)₂ SiCl₂,

(CH₂ CH₃)₂ Si(OC₂ CH₃)₂,

(CH₂ CH₃)₂ Si(O(CH₂)₂ CH₃)₂,

(CH₂ CH₃)₂ Si(OCH(CH₃)₂)₂,

(CH₂ CH₃)₂ Si(O(CH₂)₃ CH₃)₂,

(CH₂ CH₃)₂ Si(OC(CH₃)₃)₂,

(CH₂ ═CH)₂ Si(OCH₃)₂,

(CH₂ ═CH)₂ Si(OCH₂ CH₃)₂,

(CH₃ (CH₂)₂)₂ Si(OCH₃)₂,

CH₃ (CH₂)₅ Si(CH₃)(OCH₃)₂,

CH₃ (CH₂)₅ Si(CH₃)(OCH₂ CH₃)₂,

CH₃ (CH₂)₅ Si(CH₃)(O(CH₂)₂ CH₃)₂,

CH₃ (CH₂)₅ Si(CH₃)(O(CH₂)₃ CH₃)₂,

CH₃ (CH₂)₅ Si(CH₃)(OC(CH₃)₃)₂,

CH₃ (CH₂)₅ Si(CH₂ CH₃)(OCH₃)₂,

CH₃ (CH₂)₇ Si(CH₃)(OCH₂ CH₃)₂,

CH₃ (CH₂)₇ Si(CH₃)(OCH₃)₂,

Br(CH₂)₈ Si(CH₃)(OCH₃)₂,

CH₃ (CH₂)₂₁ Si(CH₃)(OCH₃)₂,

CH₃ (CH₂)₉ Si(CH₃)(OCH₃)₂,

CH₃ (CH₂)₁₁ Si(CH₃)(OCH₃)₂,

CH₃ (CH₂)₁₅ Si(CH₃)(OCH₃)₂,

CH₃ (CH₂)₁₇ Si(CH₃)(OCH₃)₂,

CH═CH(CH₂)₆ Si(CH₃)(OCH₃)₂,

F₃ C(CF₂)₅ (CH₂)₂ Si(CH₃)(OCH₃)₂,

H₂ N(CH₂)₁₁ Si(CH₃)(OCH₃)₂,

H₃ COO(CH₂)₃ Si(CH₃)(OCH₃)₂,

CH₃ COO(CH₂)₃ Si(CH₃)(OCH₃)₂,

H₂ N(CH₂)₃ OC(CH₃)₂ CH═CHSi(CH₃)(OCH₃)₂ CH₂ ═CHCOO(CH₂)₃ Si(CH₃)(OCH₃)₂,##STR24##

Silane derivatives represented by the general formula (18):

(CH₃)₃ SiCl,

(CH₃)₃ Si(NCO),

(CH₃)₃ Si(OCH₃),

(CH₃)₃ Si(OCH₂ CH₃),

(CH₃)₃ Si(O(CH₂)₂ OH₃),

(CH₃)₃ Si(OCH(CH₃)₂),

(CH₃)₃ Si(O(CH₂)₃ CH₃),

(CH₃)₃ Si(OC(CH₃)₃),

(CH₂ CH₃)₃ SiCl,

(CH₂ CH₃)₃ Si (OCH₃),

(CH₂ CH₃)₃ Si(OCH₂ CH₃),

(CH₂ CH₃)₃ Si(O(CH₂)₂ CH₃),

(CH₂ CH₃)₃ Si(OCH(CH₃)₂),

(CH₂ CH₃)₃ Si(O(CH₂)₃ CH₃),

(CH₂ CH₃)₃ Si(OC(CH₃)₃),

(CH₃ (CH₂)₂)₃ Si(OCH₃),

(CH₃ (CH₂)₂)₃ SiCl,

CH₃ (CH₂)₅ Si(CH₃)₂ OCH₃,

CH₃ (CH₂)₅ Si(CH₃)₂ (OCH₂ CH₃),

CH₃ (CH₂)₅ Si(CH₃)₂ (O(CH₂)₂ CH₃),

CH₃ (CH₂)₅ Si(CH₃)₂ (O(CH₂)₃ CH₃),

CH₃ (CH₂)₅ Si(CH₃)₂ (OC(CH₃)₃),

CH₃ (CH₂)₅ Si(CH₂ CH₃)₂ (OCH₃),

(CH₃ (CH₂)₅)₂ Si(CH₃)(OCH₃),

(CH₃ (CH₂)₅)₃ SiOCH₃,

CH₃ (CH₂)₇ Si(CH₃)₂ (OCH₃),

CH₃ (CH₂)₉ Si(CH₃)₂ (OCH₃),

CH₃ (CH₂)₁₁ Si(CH₃)₂ (OCH₃),

CH₃ (CH₂)₁₇ Si(CH₃)₂ (OCH₃),

CH═CH--(CH₂)₆ Si(CH₃)₂ (OCH₃),

CH═CHCOO(CH₂)₃ Si(CH₃)₂ (OCH₃),

CH₃ COO(CH₂)₃ Si(CH₃)₂ (OCH₃),

H₂ N(CH₂)₁₁ Si(CH₃)₂ (OCH₃),

F₃ C(CF₂)₅ (CH₂)₂ Si(CH₃)₂ (OCH₃), ##STR25##

In the present invention, at least one selected from the groupconsisting of silane compounds represented by the foregoing generalformulae (16), (17) and (18) may be preferably used in combination withat least one selected from the group consisting of metallic ornonmetallic compounds represented by the following general formulae (19)and (20):

    M.sup.1 (Y.sup.5).sub.b L.sup.1.sub.3-b                    (19)

    M.sup.2 (Y.sup.6).sub.c L.sup.2.sub.4-c                    (20)

wherein M¹ represents a trivalent atom; M² represents a tetravalent atomother than carbon atom; Y⁵ and Y⁶ may be the same or different and eachrepresent a hydrolyzable functional group or a hydroxyl group; L¹ and L²may be the same or different and each represent a chelate group or R₁₀--COO-- group (in which R₁₀ represents an alkyl group); b represents aninteger 0 to 3; and c represents an integer 0 to 4, with the provisothat when b is 3 or c is 4, the plurality of Y⁵ 's or Y⁶ 's don'trepresent a hydroxyl group at the same time.

In this case, the amount of the metallic or nonmetallic compoundrepresented by the foregoing general formula (19) or (20) to be used ispreferably in the range of 0.01 to 80 mol % based on the amount of thehigh molecular compound represented by the foregoing general formula(1).

Specific examples of the metallic or nonmetallic compounds representedby the foregoing general formulae (19) and (20) include the followingcompounds. These compounds may be used singly or in combination.Metallic or nonmetallic organic compounds represented by the generalformula (19):

Al(OCH₃)₃, Al(OCH₂ CH₃)₃,

Al(O(CH₂)₂ CH₃)₃, Al(OCH(CH₃)₂)₃,

Al(O(CH₂)₃ CH₃)₃, Al(OC(CH₃)₃)₃,

Al(OCH(CH₃)₂)₂ (OC(CH₃)₃),

Al(OC(CH₃)CHCOCH₃)₃,

Al(OC(CH₃)CHCOCH₂ CH₃)₃,

Al(OC(CH₃)CHCOCH₂ CH₃)₂ (OC(CH₃)CHCOCH₃),

AlCl₃, Al(OCH(CH₃)₂)₂ (OC(CH₃)CHCOCH₂ CH₃),

Al(OC(CH₃)₃)₂ (OC(CH₃)CHCOCH₃),

In(OCH₃)₃, In(OCH₂ CH₃)₃,

In(O(CH₂)₂ CH₃)₃, In(OCH(CH₃)₂)₃,

In(O(CH₂)₃ CH₃)₃, In(OC(CH₃)₃)₃,

As(OCH₃)₃, As(OCH₂ CH₃)₃,

As(O(CH₂)₂ CH₃)₃, As(OC(CH₃)₃)₃,

Ga(OCH₃)₃, Ga(OCH₂ CH₃)₃,

Ga(O(CH₂)₂ CH₃)₃, Ga(OC(CH₃)₃)₃,

B(OCH₃)₃, B(O(CH₂)₃ CH₃)₃,

B(OC(CH₃)₃)₃, Y(OCH₃)₃,

Y(OCH₂ CH₃)₃, Y(O(CH₂)₃ CH₃)₃,

Y(OOCCH₃)₃, Y(OC(CH₃)CHCOCH₃)₃,

YCl₃, Fe(OCH₃)₃,

Fe(O(CH₂)₃ CH₃)₃, Fe(OC(CH₃)₃)₃.

Metallic or nonmetallic organic compounds represented by the generalformula (20):

Si(OCH₃)₄, Si(OCH₂ CH₃)₄,

Si(O(CH₂)₂ CH₃)₄, Si(OCH(CH₃)₂)₄,

Si(O(CH₂)₃ CH₃)₄, Si(OC(CH₃)₃)₄,

Si(OOCCH₃)₄, Si(OOCCH₂ CH₃)₄,

Si(NCO)₄, Ge(OCH₃)₄,

Ge(O(CH₂)₂ CH₃)₄, Ge(O(CH₂)₃ CH₃)₄,

Sn(OCH₃)₄, Sn(OCH(CH₃)₂)₄,

Sn(O(CH₂)₃ CH₃)₄, Ti(OCH₃)₄,

Ti(OCH₂ CH₃)₄, Ti(O(CH₂)₂ CH₃)₄,

Ti(OCH(CH₃)₂)₄, Ti(O(CH₂)₃ CH₃)₄,

Ti(OC(CH₃)₃)₄, Ti(OOCCH₃)₄,

Ti(OOCCH₂ CH₃)₄, Ti(O(CH₂)₁₆ CH₃)₄,

Ti(OCH₂ CH(CH₂ CH₃)(CH₂)₃ CH₃)₄,

Ti(OCH(CH₃)COOH)₂ (OH)₂,

Ti(OC(CH₃)CHCOCH₃)₄,

Ti(O(CH₂)₂ CH₃)₂ (OC(CH₃)CHCOCH₃)₂,

Ti(O(CH₂)₃ CH₃)₃ (OOC(CH₂)₁₆ CH₃),

Zr(OCH₃)₄, Zr(O(CH₂)₃ CH₃)₄,

Zr(O(CH₂)₂ CH₃)₄,

Zr(OC(CH₃)CHCOCH₃)₄,

Zr(O(CH₂)₃ CH₃)₂ (OC(CH₃)CHCOCH₃)₂,

Zr(OC(CH₃)CHCOCH₂ CH₃)₄,

Zr(OCH(CH₃)COOH)₂ (O(CH₂)₃ CH₃)₂

In the eighth embodiment of the nonlinear optical element according tothe present invention, finely divided grains of a semiconductor or metalwhich exert a nonlinear optical effect are incorporated in a mediumformed of a hydrolyzate of a compound having a hydrolyzable substituentbonded to a trivalent atom or a tetravalent atom other than carbon atom.As the foregoing compound having a hydrolyzable substituent bonded to atrivalent atom or a tetravalent atom other than carbon atom there may beused at least a silane compound represented by the foregoing generalformula (8) or (8A).

This embodiment of the nonlinear optical element according to thepresent invention can be prepared by a process which comprises mixingfinely divided grains of a semiconductor or metal which exert anonlinear optical effect or a metal salt or metal complex as itsstarting material with at least a silane compound represented by theforegoing general formula (8) or (8A) among compounds having ahydrolyzable substituent bonded to a trivalent atom or a tetravalentatom other than carbon atom in the presence of a solvent, and thensubjecting the compound having a hydrolyzable substituent bonded to atrivalent atom or a tetravalent atom other than carbon atom tohydrolysis so that it is gelatinized. This embodiment of the nonlinearoptical element according to the present invention can also be preparedby a process which comprises partially hydrolyzing the moiety of acompound having a hydrolyzable substituent bonded to a trivalent atom ora tetravalent atom other than carbon atom containing a silane compoundrepresented by the foregoing general formula (8) or (8A) as an essentialcomponent which is hydrolyzed at a relatively low rate to prepare a sol,mixing the sol thus obtained, other sols of the compound having ahydrolyzable substituent bonded to a trivalent atom or a tetravalentatom other than carbon atom or a hydrolyzate thereof and finely dividedgrains of a semiconductor or metal which exert a nonlinear opticaleffect or a metal salt or metal complex as its starting material, andthen allowing the mixture to undergo hydrolysis to make a gel.

In the compound having a hydrolyzable substituent bonded to a trivalentatom or a tetravalent atom other than carbon atom in the foregoingembodiment, the trivalent and tetravalent atoms are not limited to thegroup III and IV elements in the periodic table. As such trivalent atomsthere may be used B, Al, Ga, In, Y, As, Fe, etc. As such tetravalentatoms there may be used Si, Ge, Sn, Ti, Zr, etc. As the hydrolyzablefunctional group there may be used any functional group which canundergo hydrolysis under known conditions. Typical examples of such ahydrolyzable functional group include a halogen atom, an isocyanategroup, an alkoxy group, and an acyloxy group such as an alkanoyloxygroup.

In the present invention, as the foregoing compound having ahydrolyzable substituent bonded to a trivalent atom or a tetravalentatom other than carbon atom there may be used at least a silane compoundrepresented by the foregoing general formula (8) or (8A).

In formula (8), or (8A) Y¹ is preferably an alkoxy group having 1 to 3carbon atoms or a halogen atom. Y² is preferably a halogen atom, analkyl group having 1 to 20 carbon atoms which may be substituted by anamino group, or a vinyl group which may be substituted by a halogenatom.

Examples of X¹ in the general formula (8) include organic residuesrepresented by the following structural formulae: ##STR26##

Examples of X^(1A) in the general formula (8A) include those of X in thegeneral formula (1).

Examples of X² include organic residues represented by the followingstructural formulae: ##STR27##

Examples of the hydrolyzable functional group represented by Y¹ includealkoxy group such as a methoxy group, an ethoxy group and a normal orisopropoxy group, a halogen atom such as a chlorine atom, and anisocyano group. The foregoing exemplary silane compounds can besynthesized from a dicarboxylic acid anhydride having a structurerepresented by X¹ and an amino group having a structure represented byH₂ N--X² -SiY¹ _(n) Y² _(m). These silane compounds can be used singlyor in combination.

These silane compounds have a carboxylic acid structure and an amidestructure that form a complex with various elements and inorganiccompounds. Thus, these silane compounds, in the form of solution orsolid obtained after gelatization and drying, can comprise a metal orsemiconductor or its starting material stably dissolved therein in arelatively high concentration. When subjected to heat treatment, thesesilane compounds forming a matrix undergo the following reaction:##STR28##

When this reaction occurs, the carboxylic acid and amide structurescontained in the polysiloxane compound as a matrix are eliminated,followed by the formation of an imide ring structure with the depositionof a metal or semiconductor or a compound as its starting material whichhas been dissolved coordinated to the carboxylic acid structure or amidestructure in the polysiloxane compound as a dopant. The heat treatmentcan be effected at a temperature of 30° to 400° C., preferably 70° to300° C., and for 1 minute to 5 hours, preferably 5 minutes to 3 hours,for example, as relatively low as around 200° C.

In the present invention, the hydrolyzable compound may comprise asilane compound represented by the general formula (8) or (8A) as anessential component, preferably in combination with at least oneselected from the group consisting of network-forming silane compoundsrepresented by the foregoing general formulae (16), (17) and (18). Thesecompounds can be used singly or in admixture.

In this case, the amount of the silane compound represented by theforegoing general formula (16), (17) or (18) to be used is preferably inthe range of 0.1 to 95 wt % based on the total amount of the film.

Specific examples of the silane compounds represented by the foregoinggeneral formulae (16), (17) and (18) are as set forth above.

In the present embodiment of the nonlinear optical element according tothe present invention, the foregoing hydrolyzable compound comprises asilane compound represented by the foregoing general formula (8),preferably in combination with at least one-selected from the groupconsisting of silane compounds represented by the foregoing generalformulae (16), (17) and (18) as well as at least one selected from thegroup consisting of metallic or nonmetallic compounds represented by theforegoing general formulae (19) and (20).

In this case, the amount of the metallic or nonmetallic compoundrepresented by the foregoing general formula (19) or (20) to be used ispreferably in the range of 0.1 to 95 wt % based on the total amount ofthe film.

In the ninth embodiment of the nonlinear optical element according tothe present invention, finely divided grains of a semiconductor or metalwhich exert a nonlinear optical effect are incorporated in a hydrolyzateof a polyimide compound having in its main chain or side chain a silylgroup having at least one hydrolyzable substituent. In this embodiment,the finely divided grains of a semiconductor or metal which exert anonlinear optical effect may be incorporated in a medium obtained by thedehydration condensation of the foregoing polyimide with a hydrolyzateof a compound having a hydrolyzable substituent bonded to a trivalentatom or a tetravalent atom other than carbon atom.

The present embodiment of the nonlinear optical element according to thepresent invention can be prepared by carrying out the followingsuccessive procedure to allow finely divided grains of a semiconductoror metal to be separated out:

(a) step of dissolving finely divided grains of a semiconductor or metalwhich exert a nonlinear optical effect or a metal salt or metal complexas its starting material and a polyamic acid compound having in its mainchain or side chain a silyl group having at least one hydrolyzablesubstituent in the presence of a proper solvent;

(b) step of mixing the solution thus obtained with a compound having ahydrolyzable substituent bonded to a trivalent atom or a tetravalentatom other than carbon atom or a hydrolyzate thereof to make a uniformsolution;

(c) step of allowing the hydrolyzable compound thus obtained to undergohydrolysis to gelatinize the solution; and

(d) step of removing the solvent therefrom, and then subjecting thematerial to heat treatment to allow finely divided grains of asemiconductor or metal to be separated out.

In the present invention, the polyimide compound to be used for thepreparation of an organic/inorganic composite matrix is preferably onewhich in the form of precursor can thoroughly make a solid solution of asemiconductor or its starting material and which can be thoroughlytransparent at the wavelength of light used, i.e., the wavelength atwhich finely divided grains of a semiconductor exert a great nonlinearoptical effect. Examples of such a high molecular compound include atleast those represented by the following general formulae (21) and (22):##STR29## wherein X is as defined above; X³, X⁴ and to X⁵ each representa divalent organic residue having not less than 2 carbon atoms; X⁶represents a trivalent organic residue having not less than 2 carbonatoms; R⁷ represents a hydrolyzable functional group; R⁸ and R⁹ eachrepresent a hydrolyzable functional group, saturated or unsaturatedaliphatic hydrocarbon group, saturated or unsaturated alicyclic group,aromatic hydrocarbon group, aralkyl group or heterocyclic group, whichorganic compound residues may contain substituents; and s represents areal number satisfying the relationship 0≦s<1 by mole ratio.

In formulae (21) and (22), X³, X⁴, X⁵ and X⁶ are preferably an alkylenegroup having 1 to 20 carbon atoms which may have an imino group-or anaromatic group which may be substituted by 1 to 3 substituents. When X³,X⁴, X⁵ and X⁶ have two or three benzene nuclei, the benzene nucleiconnect directly or connect via an alkylene group having 1 to 5 carbonatoms which may be substituted by an oxygen atom, an sulfur atom, SO₂,an imino group, a halogen atom. Examples of a substituent of the benzenenucleus include an alkyl group having 1 to 5 carbon atoms, an alkoxygroup having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbonatoms and a halogen atom.

R⁷ is preferably an alkoxy group having 1 to 3 carbon atoms or a halogenatom.

R⁸ and R⁹ are preferably an alkyl group having 1 to 20 carbon atomswhich may be substituted by an amino group, a vinyl group which may besubstituted by a halogen atom, a cycloalkyl group having 1 to 10 carbonatoms, a cycloalkenyl group having 1 to 10 carbon atoms or a phenylgroup which may be substituted by an alkyl group having 1 to 5 carbonatoms, an alkoxy group having 1 to 5 carbon atoms or a halogen atom.

Specific examples of X include those exemplified above. Examples of X³to X⁵ include the following compounds: ##STR30##

Examples of X⁶ include the following organic residues: ##STR31##

Examples of the hydrolyzable group R⁷ include a methoxy group, an ethoxygroup, an alkoxy group such as a normal or isopropoxy group, a halogenatom such as chlorine, and an isocyano group. Examples of R⁸ and R⁹include organic residues such as the foregoing hydrolyzable groups,alkyl groups such as a methyl group, an ethyl group and a propyl group,and aromatic groups such as a phenyl group.

These high molecular compounds, in the form of precursor, have manycarboxylic acid structures as functional groups that form a complex withvarious inorganic elements and inorganic compounds. Thus, these highmolecular compounds, in the form of solution or solid obtained bygelatinization and drying, can comprise a metal or semiconductor or itsstarting material stably dissolved therein in a relatively highconcentration. When subjected to heat treatment, these high molecularcompounds undergo the following reaction: ##STR32##

When this reaction occurs, the carboxylic acid and amide structurescontained in the high molecular compound as a matrix are eliminated,followed by the formation of an imide ring structure with the depositionof a metal or semiconductor or a compound as its starting material whichhas been dissolved coordinated to the carboxylic acid site in the highmolecular compound as a dopant. The heat treatment can be effected at atemperature of 30° to 400° C., preferably 70° to 300° C., and for 1minute to 5 hours, preferably 5 minutes to 3 hours, for example, asrelatively low as around 200° C.

In the present embodiment, the foregoing high molecular compound may beused in combination with a hydrolyzable compound. As the hydrolyzablecompound there may be preferably used at least one selected from thegroup consisting of silane compounds represented by the foregoinggeneral formulae (16), (17) and (18). These compounds may be used singlyor in admixture. In this case, the amount of the silane compoundrepresented by the foregoing general formula (16), (17) or (18) to beused is preferably in the range of 0.1 to 95 wt % based on the totalamount of the film.

In the present embodiment of the nonlinear optical element according tothe present invention, the matrix has a structure obtained by themicrostructural complexing of a polycondensation product of ahydrolyzable compound with a polyimide having a silyl group in its mainchain or side chain and thus exhibits a great flexibility as a polymerthat makes itself insusceptible to crack during the drying step.Further, the matrix contains a hard inorganic component and thusexhibits a high mechanical strength and an excellent thermal stabilityas compared with the high molecular compound free of inorganiccomponent.

In the eighth and ninth embodiments of the present invention, apreparation process may be used which comprises hydrolyzing ahydrolyzable compound to prepare a porous gel, dispersing finely dividedgrains of a semiconductor or metal in the gel so that the finely dividedgrains are adsorbed thereto, and then subjecting the gel to heattreatment to allow the finely divided grains of a semiconductor or metalto be separated out, as described in JP-A-2-230223. However, thispreparation process is disadvantageous in that it has a difficulty ofpermeability, etc., making it difficult to uniformly disperse and retainfinely divided grains of a semiconductor or metal in the medium. Thus,the following preparation process is preferably used in the presentinvention. That is, the foregoing hydrolyzable compound is added to aproper solvent, e.g., water and organic solvent such as alcohol, ether,ester, aliphatic hydrocarbon, aromatic hydrocarbon and halogenatedhydrocarbon, singly or in admixture, with a predetermined amount offinely divided grains of a semiconductor or metal to be incorporated.The mixture is then gelatinized. In order to prevent the gel fromcracking during drying, it is effectively used in admixture with a highboiling solvent such as formamide, dimethylformamide (DMF) and glycerinas a drying controlling agent. The sol thus prepared is (i) gelatinizedin a proper solution, and then dried or formed and worked into a fiber,or (ii) coated on a proper substrate, gelatinized, and then dried. Thecoating of the sol on a substrate can be accomplished by any knowncoating method such as dip coating and spin coating. In order toaccelerate the gelatinization reaction, a catalyst such as acid and basecan be used as necessary. Further, gelatinization can be assisted byheat treatment at a temperature of 30° to 1,000° C.

The nonlinear optical element according to the present invention thusformed comprises finely divided grains dispersed and retained in amatrix formed by the polycondensation of a hydrolyzable compound.

The silane compounds represented by the foregoing general formulae (8),and (16) to (20) and the foregoing metallic or nonmetallic compounds canbe arbitrarily selected so far as they don't depart from the scope ofthe present invention. In general, these compounds have differenthydrolysis rates. In the case where various hydrolyzable substanceshaving different hydrolysis rates are used, when all these hydrolyzablesubstances are mixed and then subjected to hydrolysis as in theconventional sol-gel process, the structure of the matrix thusgelatinized is determined by the component which undergoes hydrolysisreaction at a high rate, making it impossible to fully attain thedesired effects of the present invention. Thus, the present inventionpreferably employs a multi-stage hydrolysis process in which hydrolysisis effected every component. That is, a process is preferably used whichcomprises mixing silane compounds and metallic or nonmetallic compoundswhich undergo hydrolysis at a relatively low rate with water or mixtureof water and an organic solvent, stirring the mixture at a propertemperature for a desired period of time, allowing the mixture to standso that it is partially kept under hydrolysis, adding a predeterminedamount of other silane compounds and metallic or nonmetallic organiccompounds, as it is or in the form of a sol obtained by the hydrolysisthereof in a separate vessel, to the sol with finely divided grains of astarting material in admixture, and then allowing the mixture to furtherundergo hydrolysis reaction so that it is subjected to dehydrationcondensation to make a gel, whereby an excellent inorganic medium can beformed. In the nonlinear optical element according to the presentinvention, if a silane compound represented by the foregoing generalformula (8) in which some of the four hydrolyzable groups are replacedby nonhydrolyzable groups is used, three-dimensionally crosslinkednetworks are less connected in a medium retaining finely divided grains,increasing the flexibility as a polymer and hence rendering the matrixinsusceptible to crack during the drying step.

Further, if the nonlinear optical element comprises a silane compoundrepresented by the foregoing general formula (16), (17) or (18) as ahydrolyzable compound, its compatibility with a high molecular compoundis enhanced because the silane compound has a nonhydrolyzablesubstituent, making it possible to form a matrix which is more denselycomplexed. In such a matrix, the compatibility with finely dividedgrains can be changed, facilitating the deposition of finely dividedgrains at a low temperature and the control of grain diameter.

As the metallic or non-metallic compound of formula (19) or (20) is acompound capable of forming an oxide by hydrolysis and providing bondsbetween the network of silica gel or a high molecular compound-silicagel composite, which is a main component of the matrix, the resultingnonlinear optical element exhibits an enhanced mechanical strength.

As the solvent used in preparation of the nonlinear optical elements ofthe present invention is eliminated before a heat treatment or achemical treatment as described above, the amount of the solvent is notparticularly limited as long as it dissolves the matrix-formingsubstances, and metal, semiconductor or its precursor.

The heat treatment for forming the matrix of the present invention isgenerally carried out under the condition of temperature and time suchthat the matrix-forming substances are not thermally decomposed. Theheating temperature is generally not higher than 400° C., preferablyfrom 50° to 250° C., and more preferably from 100° to 200° C., and theheating time varies depending on the heating temperature and isgenerally from 10 minutes to 10 days, preferably from 1 hour to 40hours, more preferably 2 hours to 20 hours. In the case that amatrix-forming substance having a hydrolyzable group is used incombination, however, the heating temperature may be not higher than1,500° C., preferably from 50° to 1,300° C.

The chemical treatment may be effected by immersing a coated film of amixture of a matrix-forming substance and a metal, semiconductor or itsprecursor in the aforesaid solvent for chemical treatment, or by bringthe coated film into contact with the solvent vapor. When immersed, thechemical treatment can be conducted at a reflux temperature. Thechemical treatment is generally practiced in the case where the coatedfilm is deteriorated by the heat treatment, and thus the chemicaltreatment should not be conducted at an extremely high temperature andit is preferably 50° to 400° C., more preferably 100° to 200° C. Theprocessing time is generally from 10 minutes to 10 days, preferably from1 hour to 40 hours and particularly preferably from 2 hours to 20 hours.

In the present invention, as "finely divided grains of a semiconductoror metal" to be separated out in the matrix there may be used anymaterials which provide a nonlinear optical effect. Examples of suchmaterials include finely divided grains of colloid of metal such as Au,Ag, Pt and Cu, compound semiconductor such as PbS, ZnS, CdS, CdSe andCdTe, oxide semiconductor such as TiO, SnO₂, Cu₂ O, ZnO, MnO and CoO,and halide such as AgI, HgI₂, CuCl, CuBr and CuI.

As effected in the case of AgI, HgCl₂, etc., the desired semiconductormay be dissolved in a proper solvent or a high molecular solution as itis. Alternatively, an organic metal compound such as metal halide, metalnitrate, metal complex, metal alkoxide, metal carboxylate and chelatecompound as a starting material of semiconductor or metal may bedissolved in a proper solvent or a high molecular solution which is thenallowed to undergo sol-gel reaction or subjected to heat treatment sothat the semiconductor or metal compound is thermally reacted to formthe desired finely divided grains of semiconductor or metal. Further,these semiconductor or metal compound may be subjected to reduction byhydrogen, etc. or a treatment by hydrogen sulfide, etc. to chemicallychange the desired finely divided grains of semiconductor or metal.Examples of the starting material of semiconductor or metal employablein the present invention include metal halides such as AgI, HgI₂, HgCl,AuCl, NiCl, PtCl₂, CuCl, CuCl₂, FeCl₃, MoCl₅, IrCl₃ and SnCl₄, metalcomplex compounds such as HAuCl₄.4H₂ O, NaAuCl₄.2H₂ O and H₂ PtCl₄,nitrates such as AgNO₃, Hg(NO₃)₂.1/2H₂ O and Zn(NO₃)₂.6H₂ O,carboxylates such as CH₃ COOAg, Zn(CH₃ COO)₂.2H₂ O, Cu(CH₃ COO)₂.H₂ O,Mn(CH₃ COO)₂.4H₂ O, Pb(CH₃ COO)₂.3H₂ O, Cd(CH₃ COO)₂.2H₂ O, Sn(CH₃COO)₂, Co(C₈ H₁₈ O₂)₂ and Fe(C₈ H₁₈ O₂)₂, and organic metal chelatecompounds such as Fe(C₅ H₅ O₂)₂, Fe(C₅ H₅ O₂)₃ and Mn(C₅ H₅ O₂)₂.

In the nonlinear optical element according to the present invention, asa material which provides a nonlinear optical effect there may bepreferably used a cuprous halide which has excitons having a small Bohrdiameter that can be effectively confined to possibly give a greatthree-dimensional nonlinear optical effect.

Such a material may be incorporated in the system in a proportion of0.01 to 99 wt %, preferably 0.1 to 95 wt % based on the total amount ofthe film.

Further, if as finely divided grains of a semiconductor or metal thereis used a dispersion of finely divided grains of a cuprous halide whichis susceptible to denaturation by oxidation, a solution preparation stepof dissolving a cuprous halide in a solution of a high molecularcompound or hydrolyzable compound, a step of coating the solution andsubjecting the high molecular compound to heat treatment or chemicaltreatment, or a step of hydrolyzing the hydrolyzable compound andcoating the high molecular solution thus obtained on a substrate orconducting other treatments to make a film are all preferably effectedin an inert atmosphere such as nitrogen and argon. Subsequently, thesolvent is preferably removed in vacuo or in an inert atmosphere.

The present invention will be further described in the followingexamples, but the present invention should not be construed as beinglimited thereto.

EXAMPLE 1

In a stream of dried nitrogen, 0.236 g of diaminodiphenyletherrepresented by the following general formula (23) was dissolved in 7.5ml of dimethylacetamide. After complete dissolution was made, 0.314 g ofpyromellitic dianhydride represented by the general formula (24) wasgradually added to the solution. Subsequently, in a stream of driednitrogen, the mixture was slowly stirred with its temperature kept at10° to 15° C. for 1 hour. The mixture was further stirred with itstemperature kept at 20° to 25° C. for 2 hours to obtain a solution of ahigh molecular compound represented by the general formula (25). Thesolution of a high molecular compound thus obtained and a turbidcolloidal dispersion obtained by mixing 0.072 g of CuCl and 7.5 ml ofdimethylacetamide with stirring were then mixed. As a result, thesolution turned to a light green transparent liquid in which CuCl hadbeen dissolved. The foregoing mixing procedures were all effected in anatmosphere of dried nitrogen.

The solution was then spin-coated on a glass substrate in theatmosphere. The coated material was heated to a temperature of 70° C.for 30 minutes in vacuo under a reduced pressure of 1 Torr, and thenkept for 30 minutes so that the solvent was removed therefrom to obtaina light green transparent film. This film was then subjected to heattreatment at a temperature of 200° C. for 30 minutes under anitrogen-stream of 200 ml/min. FIG. 1 illustrates the change of infraredabsorption spectrum by heat treatment wherein FIG. 1(a) illustrates theinfrared absorption spectrum before heat treatment and FIG. 1(b)illustrates the infrared absorption spectrum after heat treatment. Theseresults show that the heat treatment involves the change of the matrixfrom the high molecular compound represented by the general formula (25)to the high molecular compound represented by the general formula (26).When the matrix was examined by X-ray diffractometry using CuKa rays forthe presence of deposit, it was confirmed that Cu₂ O had been depositedby the heat treatment. The grain diameter of the deposit was found to be10 to 50 nm under a transmission electron microscope. The high molecularcompound/Cu₂ O composite film thus obtained contained a deposit having asufficiently small grain diameter and thus assumed transparent andbrown. ##STR33## wherein n' is about 500.

EXAMPLE 2

In a stream of dried nitrogen, 0.236 g of diaminodiphenyletherrepresented by the following general formula (23) was dissolved in 7.5ml of dimethylacetamide. After complete dissolution was made, 0.314 g ofpyromellitic dianhydride represented by the general formula (24) wasgradually added to the solution. Subsequently, in a stream of driednitrogen, the mixture was slowly stirred with its temperature kept at10° to 15° C. for 1 hour. The mixture was further stirred with itstemperature kept at 20° to 25° C. for 2 hours to obtain a solution of ahigh molecular compound represented by the general formula (25). Thesolution of a high molecular compound thus obtained and a turbidcolloidal dispersion obtained by mixing 0.080 g of tetrachloroauric acidand 7.5 ml of dimethylacetamide with stirring were then mixed to obtaina light orange transparent liquid. The foregoing mixing procedures wereall effected in an atmosphere of dried nitrogen.

The solution was then spin-coated on a glass substrate in theatmosphere. The coated material was heated to a temperature of 70° C.for 30 minutes in vacuo under a reduced pressure of 1 Torr, and thenkept for 30 minutes so that the solvent was removed therefrom to obtaina light yellow transparent film. This film was then subjected to heattreatment at a temperature of 200° C. for 30 minutes in the atmosphere.FIG. 1 illustrates the change of infrared absorption spectrum by heattreatment. When the material was examined by X-ray diffractometry forthe presence of Au, it was confirmed that Au had been deposited by theheat treatment. The grain diameter of the deposit was found to be 5 to20 nm under a transmission electron microscope. The high molecularcompound/Au composite film thus obtained contained a deposit having asufficiently small grain diameter and thus assumed transparent and redpurple. The absorption spectrum shows that the material has a broad peakabsorption at 570 nm. This absorption corresponds to the wavelength ofplasma oscillation of metal grains. This shows that the material thusprepared can be thoroughly used as a nonlinear optical element.

EXAMPLE 3

In a stream of dried nitrogen, 1.028 g of 2,2-bis4-(4-aminophenoxy)phenyl!hexafluoropropane represented by the followinggeneral formula (27) was dissolved in 7.5 ml of dimethylacetamide. Aftercomplete dissolution was made, 0.888 g of4,4'-(hexafluoroisopropyridene)phthalic anhydride represented by thegeneral formula (28) was gradually added to the solution. Subsequently,in a stream of dried nitrogen, the mixture was slowly stirred with itstemperature kept at 10° to 15° C. for 1 hour. The mixture was furtherstirred with its temperature kept at 20° to 25° C. for 2 hours to obtaina solution of a high molecular compound represented by the generalformula (29). The solution of a high molecular compound thus obtainedand a solution obtained by mixing 0.080 g of tetrachloroauric acid and7.5 ml of dimethylacetamide were then mixed to obtain a light orangetransparent solution. The foregoing mixing procedures were all effectedin an atmosphere of dried nitrogen.

The solution was then spin-coated on a glass substrate in theatmosphere. The coated material was heated to a temperature of 70° C.for 30 minutes in vacuo under a reduced pressure of 1 Torr, and thenkept for 30 minutes so that the solvent was removed therefrom to obtaina light yellow transparent film (general formula (30)). This film wasthen subjected to heat treatment at a temperature of 200° C. for 30minutes in the atmosphere. When the material was examined by X-raydiffractometry for the presence of deposit, it was confirmed that Au hadbeen deposited by the heat treatment. The grain diameter of the depositwas found to be 5 to 15 nm under a transmission electron microscope. Thehigh molecular compound/Au composite film thus obtained contained adeposit having a sufficiently small grain diameter and thus assumedtransparent and red purple. ##STR34## wherein n" is about 300.

EXAMPLE 4

In a stream of dried nitrogen, a dispersion obtained by mixing 0.035 gof CuCl, 0.02 g of dicyandiamide and 7.5 ml of dimethylacetamide withstirring and 2.0 g of a bisphenol A type epoxy resin (trade name:Epicoat 562, available from Shell) were mixed to obtain a light greentransparent liquid. The foregoing mixing procedures were all effected inan atmosphere of dried nitrogen. The solution was then spin-coated on aglass substrate in the atmosphere. The coated material was heated to atemperature of 70° C. in the atmosphere, and then kept for 60 minutes sothat the solvent was removed therefrom to obtain a light yellowtransparent film. This film was then subjected to heat treatment at atemperature of 200° C. for 30 minutes under a nitrogen-stream of 200ml/min. When the material was examined by X-ray diffractometry for thepresence of deposit, it was confirmed that Cu₂ O had been deposited. Thehigh molecular compound/Cu₂ O composite film thus obtained contained adeposit having a sufficiently small grain diameter and thus assumedtransparent and brown.

EXAMPLE 5

In a stream of dried nitrogen, 0.236 g of diaminodiphenyletherrepresented by the foregoing general formula (23) was dissolved in 7.5ml of dimethylacetamide. After complete dissolution was made, 0.314 g ofpyromellitic dianhydride represented by the foregoing general formula(24) was gradually added to the solution. Subsequently, in a stream ofdried nitrogen, the mixture was slowly stirred with its temperature keptat 10° to 15° C. for 1 hour. The mixture was further stirred with itstemperature kept at 20° to 25° C. for 2 hours to obtain a solution of ahigh molecular compound represented by the foregoing general formula(25). The solution of a high molecular compound thus obtained and aturbid colloidal dispersion obtained by mixing 0.065 g of CuCl and 7.5ml of dimethylacetamide with stirring were then mixed. As a result, thesolution turned to a light green transparent liquid in which CuCl hadbeen dissolved. The foregoing mixing procedures were all effected in anatmosphere of dried nitrogen.

The solution was then spin-coated on a glass substrate in an atmosphereof dried nitrogen. The coated material was heated to a temperature of70° C. for 30 minutes in vacuo under a reduced pressure of 1 Torr, andthen kept for 30 minutes so that the solvent was removed therefrom toobtain a colorless transparent film. This film was then subjected toheat treatment at a temperature of 200° C. for 30 minutes in vacuo undera reduced pressure of 1×10⁻⁵ Torr. FIG. 1 illustrates the change ofinfrared absorption spectrum by heat treatment wherein FIG. 1(a)illustrates the infrared absorption spectrum before heat treatment andFIG. 1(b) illustrates the infrared absorption spectrum after heattreatment. These results show that the heat treatment involves thechange of the matrix from the high molecular compound represented by theforegoing general formula (25) to the high molecular compoundrepresented by the foregoing general formula (26). When the matrix wasexamined by X-ray diffractometry for the presence of deposit, it wasconfirmed that CuCl had been deposited by the heat treatment. The graindiameter of the deposit was found to be 5 to 50 nm under a transmissionelectron microscope. The high molecular compound/CuCl composite filmthus obtained contained a deposit having a sufficiently small graindiameter and thus assumed transparent and light yellow.

EXAMPLE 6

In a stream of dried nitrogen, 0.236 g of diaminodiphenyletherrepresented by the foregoing general formula (23) was dissolved in 7.5ml of dimethylacetamide. After complete dissolution was made, 0.314 g ofpyromellitic dianhydride represented by the foregoing general formula(24) was gradually added to the solution. Subsequently, in a stream ofdried nitrogen, the mixture was slowly stirred with its temperature keptat 10° to 15° C. for 1 hour. The mixture was further stirred with itstemperature kept at 20° to 25° C. for 2 hours to obtain a solution of ahigh molecular compound represented by the foregoing general formula(5). The solution of a high molecular compound thus obtained and aturbid colloidal dispersion obtained by mixing 0.094 g of CuBr and 7.5ml of dimethylacetamide with stirring were then mixed. As a result, thesolution turned to a light green transparent liquid. The foregoingmixing procedures were all effected in an atmosphere of dried nitrogen.

The solution was then spin-coated on a glass substrate in an atmosphereof dried nitrogen. The coated material was heated to a temperature of70° C. for 30 minutes in vacuo under a reduced pressure of 1 Torr, andthen kept for 30 minutes so that the solvent was removed therefrom toobtain a light green transparent film. This film was then subjected toheat treatment at a temperature of 200° C. for 30 minutes in vacuo undera reduced pressure of 1×10⁻⁵ Torr. When the material was examined byX-ray diffractometry for the presence of deposit, it was confirmed thatCuBr had been deposited by the heat treatment. The grain diameter of thedeposit was found to be 5 to 50 nm under a transmission electronmicroscope. The high molecular compound/CuCl composite film thusobtained contained a deposit having a sufficiently small grain diameterand thus assumed transparent and yellow.

EXAMPLE 7

In a stream of dried nitrogen, 1.028 g of 2,2-bis4-(4-aminophenoxy)phenyl!hexafluoropropane represented by the foregoinggeneral formula (27) was dissolved in 37.5 ml of dimethylacetamide.After complete dissolution was made, 0.888 g of4,4'-(hexafluoroisopropyridene)phthalic anhydride represented by theforegoing general formula (28) was gradually added to the solution.Subsequently, in a stream of dried nitrogen, the mixture was slowlystirred with its temperature kept at 10° to 15° C. for 1 hour. Themixture was further stirred with its temperature kept at 20° to 25° C.for 2 hours to obtain a solution of a high molecular compoundrepresented by the foregoing general formula (29). The solution of ahigh molecular compound thus obtained and a solution obtained by mixing0.099 g of CuCl and 37.5 ml of dimethylacetamide were then mixed toobtain a light blue transparent solution. The foregoing mixingprocedures were all effected in an atmosphere of dried nitrogen.

The solution was then spin-coated on a glass substrate in an atmosphereof dried nitrogen. The coated material was heated to a temperature of70° C. for 30 minutes in vacuo under a reduced pressure of 1 Torr, andthen kept for 30 minutes so that the solvent was removed therefrom toobtain a colorless transparent film. This film was then subjected toheat treatment at a temperature of 200° C. for 30 minutes in vacuo undera reduced pressure of 1×10⁻⁵ Torr (the foregoing general formula (30)).When the material was examined by X-ray diffractometry for the presenceof deposit, it was confirmed that CuCl had been deposited by the heattreatment (see FIG. 2). The grain diameter of the deposit was found tobe 10 to 50 nm under a transmission electron microscope. The highmolecular compound/CuCl composite film thus obtained contained a deposithaving a sufficiently small grain diameter and thus assumed transparentand light yellow. FIG. 3 illustrates the absorption spectrum of thisfilm. A CuCl excimer absorption sub-band structure is found at 370 nm.

Then, the CuCl fine grain-dispersed thin film thus obtained was measuredwith respect to the nonlinear susceptibility χ.sup.(3) using an opticalapparatus shown in FIG. 9 according to the degenerate four-light wavemixing method. As a result, the value of χ.sup.(3) was very high,5.4×10⁻⁸ esu.

In the measurement of the nonlinear susceptibility, a Nd: YAG laser wasused as a light source, and its 4th harmonic (266 nm) was applied asexcitation light to β-BaB₂ O₄ (BBO) crystals in an optical parametricoscillator (OPO) to adjust a light wavelength for each tested sample. Asshown in FIG. 9, an outgoing beam from OPO is divided by a half mirrorto two pump lights and one probe light which are impinged into a samplewhereupon a signal light is generated. The value of χ.sup.(3) iscalculated from light strength of the signal light measured by aphotomultiplier (PMT).

EXAMPLE 8

In a stream of dried nitrogen, 1.028 g of 2,2-bis4-(4-aminophenoxy)phenyl!hexafluoropropane represented by the foregoinggeneral formula (27) was dissolved in 37.5 ml of dimethylacetamide.After complete dissolution was made, 0.888 g of4,4'-(hexafluoroisopropyridene)-2-phthalic anhydride represented by theforegoing general formula (28) was gradually added to the solution.Subsequently, in a stream of dried nitrogen, the mixture was slowlystirred with its temperature kept at 10° to 15° C. for 1 hour. Themixture was further stirred with its temperature kept at 20° to 25° C.for 2 hours to obtain a solution of a high molecular compoundrepresented by the foregoing general formula (29). The solution of ahigh molecular compound thus obtained and a solution obtained by mixing0.142 g of CuBr and 37.5 ml of dimethylacetamide with stirring were thenmixed to obtain a light blue transparent solution. The foregoing mixingprocedures were all effected in an atmosphere of dried nitrogen.

The solution was then spin-coated on a glass substrate in an atmosphereof dried nitrogen. The coated material was heated to a temperature of70° C. in vacuo under a reduced pressure of 1 Torr, and then kept at thesame temperature for 30 minutes so that the solvent was removedtherefrom to obtain a colorless transparent film. This film was thensubjected to heat treatment at a temperature of 200° C. for 30 minutesunder a reduced pressure of 1×10⁻⁵ Torr (the foregoing general formula(30)). When the material was examined by X-ray diffractometry for thepresence of deposit, it was confirmed that CuBr had been deposited bythe heat treatment (see FIG. 4). The grain diameter of the deposit wasfound to be 15 to 50 nm under a transmission electron microscope. Thehigh molecular compound/CuBr composite film thus obtained contained adeposit having a sufficiently small grain diameter and thus assumedtransparent and light yellow. FIG. 5 illustrates the absorption spectrumof this film. A CuBr excimer absorption sub-band structure is found at380 nm and 415 nm.

Then the CuBr fine grain-dispersed thin film thus obtained was measuredwith respect to the nonlinear susceptibility χ.sup.(3) using theapparatus as shown in FIG. 9 wherein the light wavelength was adjustedto 420 nm. The value of χ.sup.(3) was very high, 9.5×10⁻⁹ esu.

EXAMPLE 9

In a stream of dried nitrogen, 0.236 g of diaminodiphenyletherrepresented by the foregoing general formula (23) was dissolved in 7.5ml of dimethylacetamide. After complete dissolution was made, 0.314 g ofpyromellitic dianhydride represented by the foregoing general formula(24) was gradually added to the solution. Subsequently, in a stream ofdried nitrogen, the mixture was slowly stirred with its temperature keptat 10° to 15° C. for 1 hour. The mixture was further stirred with itstemperature kept at 20° to 25° C. for 2 hours to obtain a solution of ahigh molecular compound represented by the foregoing general formula(25). The solution of a high molecular compound thus obtained and aturbid colloidal dispersion obtained by mixing 0.065 g of CuCl and 7.5ml of dimethylacetamide with stirring were then mixed. As a result, CuClwas dissolved in the solution, and the mixture then turned to a lightgreen transparent liquid. The foregoing mixing procedures were alleffected in an atmosphere of dried nitrogen.

The solution was then spin-coated on a glass substrate in an atmosphereof dried nitrogen. The coated material was heated to a temperature of70° C. in vacuo under a reduced pressure of 1 Torr, and then kept at thesame temperature for 60 minutes so that the solvent was removedtherefrom to obtain a light green transparent film. This film was thensubjected to heat treatment at a temperature of 200° C. for 30 minutesin vacuo under a reduced pressure of 1×10⁻⁵ Torr. When the material wasexamined by X-ray diffractometry for the presence of deposit, it wasconfirmed that CuCl had been deposited by the heat treatment. The highmolecular compound/CuCl composite film thus obtained contained a deposithaving a sufficiently small grain diameter and thus assumed transparentand brown.

EXAMPLE 10

In a stream of dried nitrogen, 0.235 g of diamino-diphenyletherrepresented by the foregoing general formula (23) was dissolved in 15 mlof dimethylacetamide. After complete dissolution was made, 0.315 g ofpyromellitic dianhydride represented by the foregoing general formula(24) was gradually added to the solution. Subsequently, in a stream ofdried nitrogen, the mixture was slowly stirred with its temperature keptat 10° to 15° C. for 1 hour. The mixture was further stirred with itstemperature kept at 20° to 25° C. for 2 hours to obtain a solution of ahigh molecular compound represented by the foregoing general formula(25). The solution of a high molecular compound thus obtained and 0.07 gof CuCl were mixed with stirring to obtain a light green transparentliquid. The foregoing mixing procedures were all effected in anatmosphere of dried nitrogen. The solution was then spin-coated on aglass substrate in an atmosphere of dried nitrogen. The coated materialwas heated to a temperature of 70° C. for 30 minutes in vacuo under areduced pressure of 1 Torr, and then kept for 30 minutes so that thesolvent was removed therefrom to obtain a light green transparent film.The glass substrate with this film was then dipped in a 4:3.5:8(volumetric ratio) of acetic anhydride, pyridine and benzene in anatmosphere of dried nitrogen for 12 hours. An infrared absorptionspectrum measurement showed that the heat treatment had involved thechange of the matrix from a high molecular compound represented by thegeneral formula (25) to a high molecular compound represented by thegeneral formula (26). When the material was examined by X-raydiffractometry for the presence of deposit, the deposition of CuCl wasobserved in the material which had been subjected to chemical treatment.The film thus obtained contained a deposit having a sufficiently smallgrain diameter and thus assumed transparent and light brown.

EXAMPLE 11

In a stream of dried nitrogen, 1.028 g of 2,2-bis4-(4-aminophenoxy)phenyl!hexafluoropropane represented by the foregoinggeneral formula (27) was dissolved in 35 ml of dimethylacetamide. Aftercomplete dissolution was made, 0.888 g of4,4'-(hexafluoroisopropyridene)-2-phthalic anhydride represented by theforegoing general formula (28) was gradually added to the solution.Subsequently, in a stream of dried nitrogen, the mixture was slowlystirred with its temperature kept at 10° to 15° C. for 1 hour. Themixture was further stirred with its temperature kept at 20° to 25° C.for 2 hours to obtain a solution of a high molecular compoundrepresented by the foregoing general formula (29). The solution of ahigh molecular compound thus obtained and 0.15 g of CuCl were mixed withstirring to obtain a light blue transparent liquid. The foregoing mixingprocedures were all effected in an atmosphere of dried nitrogen. Thesolution was then spin-coated on a glass substrate in an atmosphere ofdried nitrogen. The coated material was heated to a temperature of 70°C. in vacuo under a reduced pressure of 1 Torr, and then kept at thesame temperature for 30 minutes so that the solvent was removedtherefrom to obtain a light blue transparent film. This film was thensubjected to chemical treatment in the same manner as in Example 10.When the material was examined by X-ray diffractometry for the presenceof deposit, the deposition of CuCl was observed. The film thus obtainedcontained a deposit having a sufficiently small grain diameter and thusassumed transparent and colorless. FIG. 6 illustrates the absorptionspectrum of this film. A CuCl excimer absorption sub-band structure isfound at 370 nm.

EXAMPLE 12

In a stream of dried nitrogen, 0.20 g of a poly-p-aminostyrene(synthesized by the method described in C. Kotlarchik and L. M. Minsk,"J. Polymer Sci. Polym. Chem.", Ed., 13, 1743 (1975)) was dissolved in10 ml of dimethylformamide. 0.25 g of phthalic anhydride was thengradually added to the solution under cooling with stirring. The mixturewas then stirred for 3 hours. The high molecular compound solution thusobtained was mixed with a turbid colloidal dispersion obtained by mixing0.072 g of CuCl with 7.5 ml of dimethylformamide to obtain a mixture ofa high molecular compound and CuCl. The foregoing mixing procedures wereall effected in an atmosphere of dried nitrogen. The solution thusobtained was then spin-coated on a glass substrate in an atmosphere ofdried nitrogen. The coated material was then heated to a temperature of70° C. for 30 minutes and 10° C. for 30 minutes in vacuo under a reducedpressure of 1 Torr to obtain a film. When this film was observed under atransmission electron microscope, finely divided grains having a size ofseveral nanometers to scores of nanometers were observed to be separatedout.

EXAMPLE 13

In a stream of dried nitrogen, 0.20 g of a poly-p-aminostyrene wasdissolved in 10 ml of dimethylformamide. 0.36 g of pyromelliticdianhydride was gradually added to the solution with stirring. Themixture was then stirred for 24 hours. The high molecular compoundsolution thus obtained was then mixed with 0.17 g of p-toluidine. Themixture was then stirred for 3 hours. The high molecular compoundsolution was then mixed with a solution obtained by mixing 0.080 g oftetrachloroauric acid with 7.5 ml of dimethylacetamide with stirring toobtain a coating solution. The foregoing mixing procedures were alleffected in an atmosphere of dried nitrogen. The coating solution wasthen spin-coated on a glass substrate in the atmosphere. The coatedmaterial was then heated to a temperature of 70° C. for 30 minutes and160° C. for 30 minutes in vacuo under a reduced pressure of 1 Torr toobtain a film. When this film was measured for absorption spectrum, apeak absorption was found in the vicinity of 570 nm. This absorptioncorresponds to the frequency of plasma oscillation of metal grains. Thisshowed that the material thus prepared can be thoroughly used as anonlinear optical material. When the material was examined for thepresence of deposit under a transmission electron microscope, grainshaving a size of several nanometers to scores of nanometers wereobserved to be separated out.

EXAMPLE 14

A film was prepared in the same manner as in Example 12 except that 0.01g of a polyamide-imide represented by the general formula (31)(synthesized by the method described in C. J. Huang, et al., "J. Appl.Polym. Sci.", 42, 2267 (1991)) was added to the high molecular compoundsolution. The film was observed under a transmission electronmicroscope. As a result, finely divided grains having a size of severalnanometers to scores of nanometers were observed to be separated out.##STR35##

EXAMPLE 15

A film was prepared in the same manner as in Example 13 except that4,4'-diaminodiphenylether was used instead of p-toluidine. The film wasobserved under a transmission electron microscope. As a result, finelydivided grains having a size of several nanometers to scores ofnanometers were observed to be separated out.

Comparative Example 1

In a stream of dried nitrogen, a dimethylformamide solution of apolystyrene was mixed with a turbid colloidal dispersion obtained bymixing CuCl with dimethylformamide with stirring to prepare a solution.The solution was then used to prepare a film. However, this film had apoor transparency.

EXAMPLE 16

In a stream of dried nitrogen, a turbid colloidal dispersion obtained bymixing 0.072 g of CuCl with 7.5 ml of dimethylformamide with stirringwas added to a solution of 0.20 g of the same poly-p-aminostyrene asused in Example 12 in 10 ml of dimethylformamide with stirring to obtaina mixture of a high molecular compound and CuCl. To the mixture wasadded diglycidylether of bisphenol A in an amount of half the equal partof the poly-p-aminostyrene. The solution thus obtained was thenspin-coated on a glass substrate in an atmosphere of dried nitrogen. Thecoat thus obtained was then heated to a temperature of 70° C. for 1 hourand 120° C. for 30 minutes in vacuo to obtain a film. When the film wasobserved under a transmission electron microscope, finely divided grainshaving a size of several nanometers to scores of nanometers wereobserved to be separated out.

EXAMPLE 17

In a stream of dried nitrogen, 0.20 g of a polycarbonate represented bythe following general formula (32) (80:20 copolymer of diphenolic acidand bisphenol A) was dissolved in 10 ml of dimethylformamide. A solutionobtained by mixing 0.080 g of tetrachloroauric acid with 7.5 ml ofdimethylacetamide with stirring was added to the solution with stirring.To the solution was then added a 1:5 mixture ofhexamethylene-1,6-diisocyanate and methylphenylisocyanate in an amountof the equal part of the carboxylic group in the polycarbonate toprepare a coating solution. The solution thus obtained was thenspin-coated on a glass substrate. The coat thus obtained was then heatedto a temperature of 70° C. for 1 hour and 120° C. for 30 minutes invacuo under a reduced pressure of 1 Torr to obtain a film. When the filmwas measured for absorption spectrum, a peak absorption was found in thevicinity of 570 nm. This peak absorption corresponds to the frequency ofplasma oscillation of metal grains. This showed that the material thusprepared can be thoroughly used as a nonlinear optical material. Whenthe material was examined for the presence of deposit under atransmission electro n microscope, finely divided grains having a sizeof several nanometers to scores of manometers were observed to beseparated out. ##STR36##

EXAMPLE 18

A film was prepared in the same manner as in Example 16 except that apolycarbonate represented by the foregoing general formula (31) was usedinstead of the poly-p-aminostyrene. The film was observed under atransmission electron microscope for the presence of deposit. As aresult, finely divided grains having a size of several nanometers toscores of nanometers were observed to be separated out.

EXAMPLE 19

A film was prepared in the same manner as in Example 17 except that 0.01g of a polyamide-imide represented by the foregoing general formula (31)was added to the high molecular compound solution. The film was observedunder a transmission electron microscope. As a result, finely dividedgrains having a size of several nanometers to scores of nanometers wereobserved to be separated out.

EXAMPLE 20

A film was prepared in the same manner as in Example 16 except that CuBrwas used instead of CuCl. The film was observed under a transmissionelectron microscope. As a result, finely divided grains having a size ofseveral nanometers to scores of nanometers were observed to be separatedout.

EXAMPLE 21

A film was prepared in the same manner as in Example 17 except that ahigh molecular compound (50:50 copolymer) represented by the followinggeneral formula (33) was used instead of the polycarbonate. The film wasobserved under a transmission electron microscope. As a result, finelydivided grains having a size of several nanometers to scores ofnanometers were observed to be separated out. ##STR37##

EXAMPLE 22

In a stream of dried nitrogen, 0.3 g of a compound represented by thefollowing general formula (34) (synthesized by the method described inM. H. Kailani, et al., "Macromoleculaes", 25, 3751 (1992)) was dissolvedin a solution of 0.6 g of the polyamide-imide represented by theforegoing general formula (31) in 15 ml of dimethylformamide. Thesolution thus obtained was then mixed with 0.4 g of CuCl with stirringto obtain a light green transparent liquid. The solution thus obtainedwas then spin-coated on a glass substrate in an atmosphere of driednitrogen. The coated material was heated to a temperature of 70° C. for30 minutes in vacuo under a reduced pressure of 1 Torr, and then kept atthe same temperature for 30 minutes so that the solvent was removedtherefrom to obtain a light green transparent film. This film was heatedto a temperature of 150° C. in vacuo under a reduced pressure of 1×10⁻⁵Torr, and then kept at the same temperature for 1 hour. When this filmwas examined for the presence of deposit by X-ray diffractometry, thedeposition of CuCl crystal was observed. When this film was measured forthe grain diameter of the deposit under a transmission electronmicroscope, finely divided grains having a size of several nanometers toscores of nanometers were observed to be separated out. When this filmwas measured for absorption spectrum, a CuCl exiton absorption sub-bandstructure was found at 370 nm. ##STR38##

EXAMPLE 23

In a stream of dried nitrogen, 0.3 g of a compound represented by thefollowing general formula (34) was dissolved in a solution of 0.6 g ofthe polyamide-imide represented by the foregoing general formula (31) in15 ml of dimethylformamide. The solution thus obtained was then mixedwith 0.4 g of CuCl with stirring to obtain a light green transparentliquid. The solution thus obtained was then spin-coated on a glasssubstrate in an atmosphere of dried nitrogen. The coated material washeated to a temperature of 70° C. for 30 minutes in vacuo under areduced pressure of 1 Torr, and then kept at the same temperature for 30minutes so that the solvent was removed therefrom to obtain a lightgreen transparent film. The glass substrate with this film was thendipped in a 4:3.5:8 (volumetric acid) of acetic anhydride, pyridine andbenzene in a stream of dried nitrogen for 12 hours. When this film wasexamined for the presence of deposit by X-ray diffractometry, thedeposition of CuCl crystal was observed. When this film was measured forthe grain diameter of the deposit under a transmission electronmicroscope, finely divided grains having a size of several nanometers toscores of nanometers were observed to be separated out. When this filmwas measured for absorption spectrum, a CuCl excimer absorption sub-bandstructure was found at 370 nm.

EXAMPLE 24

In a stream of dried nitrogen, 0.1 g of a compound represented by theforegoing general formula (34) was dissolved in a solution of 0.6 g ofpolycarbonate resin (molecular weight: 21,000) having a repeating unitrepresented by the following formula (35) in 15 ml of dimethylformamide.The solution thus obtained was then mixed with 0.05 g of CuCl withstirring to obtain a light green transparent liquid. The solution thusobtained was then spin-coated on a glass substrate in an atmosphere ofdried nitrogen. The coated material was heated to a temperature of 70°C. for 30 minutes in vacuo under a reduced pressure of 1 Torr, and thenkept at the same temperature for 30 minutes so that the solvent wasremoved therefrom to obtain a pale blue transparent film. This film washeated to a temperature of 150° C. in vacuo under reduced pressure of1×10⁻⁵ Torr, and then kept at the same temperature for 1 hour. When thisfilm was examined for the presence of deposit by X-ray diffractometry,the deposition of CuCl crystal was observed. When this film was measuredfor the grain diameter of the deposit under a transmission electronmicroscope, finely divided grains having a size of several nanometers toscores of nanometers were observed to be separated out. When this filmwas measured for absorption spectrum, a CuCl exiton absorption sub-bandstructure was found at 370 nm. ##STR39##

EXAMPLE 25

In a stream of dried nitrogen, 0.3 g of a compound represented by thefollowing general formula (34) was dissolved in a solution of 0.6 g ofthe polyamide-imide represented by the foregoing general formula (31) in15 ml of dimethylformamide. The solution thus obtained was then mixedwith 0.1 g of tetrachloroauric acid with stirring to obtain a lightorange transparent liquid. The solution thus obtained was thenspin-coated on a glass substrate in a stream of dried nitrogen. Thecoated material was heated to a temperature of 70° C. for 30 minutes invacuo under a reduced pressure of 1 Torr, and then kept at the sametemperature for 30 minutes so that the solvent was removed therefrom toobtain a light yellow transparent film. This film was heated to atemperature of 250° C. in the atmosphere, and then kept at the sametemperature for 1 hour. When this film was measured for the graindiameter of the deposit under a transmission electron microscope, finelydivided grains having a size of several nanometers to scores ofnanometers were observed to be separated out. When this film wasmeasured for absorption spectrum, a broad absorption with its peakcentered at 570 nm was observed. This absorption corresponds to thefrequency of plasma oscillation of metal grains. This showed that thematerial thus prepared can be thoroughly used as a nonlinear opticalmaterial.

Comparative Example 2

In a stream of dried nitrogen, a solution of 0.6 g of a polycarbonateresin consisting of repeating structure units represented by theforegoing general formula (35) (molecular weight: 21,000) in 15 ml ofdimethylformamide was mixed with 0.05 g of CuCl. As a result, a turbidgreen liquid was obtained. Thus, CuCl could not be thoroughly dissolvedin the solution.

EXAMPLE 26

In a stream of dried nitrogen, 30 ml of a 20% aqueous solution of a highmolecular compound having an intrinsic viscosity of 0.95 dl/g at atemperature of 30° C. in the water consisting of repeating structureunits represented by the following general formula (36) was mixed with0.05 g of CuCl to obtain a light green transparent liquid. The solutionthus obtained was then spin-coated on a glass substrate in an atmosphereof dried nitrogen. The coated material was heated to a temperature of70° C. in vacuo under a reduced pressure of 1 Torr, and then kept at thesame temperature for 30 minutes so that the solvent was removedtherefrom to obtain a light green transparent film. The glass substratewith this film was exposed to hydrogen chloride gas in an atmosphere ofdried nitrogen for 1 hour. When the material was examined for thepresence of deposit by X-ray diffractometry, the deposition of CuCl wasobserved. This film contained a deposit having a sufficiently smallgrain diameter and thus assumed transparent and light green. ##STR40##

EXAMPLE 27

In a stream of dried nitrogen, 30 ml of a 20% aqueous solution of a highmolecular compound consisting of repeating structure units representedby the foregoing general formula (36) was mixed with 0.05 g of CuBr toobtain a light green transparent liquid. The solution thus obtained wasthen spin-coated on a glass substrate in an atmosphere of driednitrogen. The coated material was heated to a temperature of 70° C. invacuo under a reduced pressure of 1 Torr, and then kept at the sametemperature for 30 minutes so that the solvent was removed therefrom toobtain a light green transparent film. The glass substrate with thisfilm was exposed to hydrogen chloride gas in an atmosphere of driednitrogen for 1 hour. When the material was examined for the presence ofdeposit by X-ray diffractometry, the deposition of CuBr was observed.This film contained a deposit having a sufficiently small grain diameterand thus assumed transparent and light green.

EXAMPLE 28

In a stream of dried nitrogen, 30 ml of a 20% aqueous solution of a highmolecular compound consisting of repeating structure units representedby the foregoing general formula (36) was mixed with 0.05 g of CuCl toobtain a light green transparent liquid. The solution thus obtained wasthen spin-coated on a glass substrate in an atmosphere of driednitrogen. The coated material was heated to a temperature of 70° C. invacuo under a reduced pressure of 1 Torr, and then kept at the sametemperature for 30 minutes so that the solvent was removed therefrom toobtain a light green transparent film. The glass substrate with thisfilm was exposed to acetic acid vapor in an atmosphere of dried nitrogenfor 1 hour. When the material was examined for the presence of depositby X-ray diffractometry, the deposition of CuCl was observed. This filmcontained a deposit having a sufficiently small grain diameter and thusassumed transparent and light green.

EXAMPLE 29

In a stream of dried nitrogen, 5 g of a high molecular compoundconsisting of repeating structure units represented by the followinggeneral formula (37) synthesized by the method described in L. J.Guilbault, M. Murano, H. J. Harwood, "J. Macromol: Sci. Chem. A", 7,1065 (1973) was dissolved in 30 ml of dimethylformamide. To the solutionwas then added 0.05 g of CuCl with stirring to obtain a light greentransparent liquid. The solution thus obtained was then spin-coated on aglass substrate in the atmosphere. The coated material was heated to atemperature of 70° C. in vacuo under a reduced pressure of 1 Torr, andthen kept at the same temperature for 30 minutes so that the solvent wasremoved therefrom to obtain a light green transparent film. When thematerial was examined for the presence of deposit by X-raydiffractometry, the deposition of CuCl was observed. This film containeda deposit having a sufficiently small grain diameter and thus assumedtransparent and light green. The grain material of the deposit was foundto be from 50 to 200 Å under a transmission electron microscope.##STR41## wherein the intrinsic viscosity is 1.0 dl/g.

EXAMPLE 30

In a stream of dried nitrogen, 5 g of a high molecular compoundrepresented by the foregoing general formula (37) was dissolved in 30 mlof dimethylformamide. To the solution was then added 0.07 g of CuBr withstirring to obtain a light green transparent liquid. The solution thusobtained was then spin-coated on a glass substrate in the atmosphere.The coated material was heated to a temperature of 70° C. in vacuo undera reduced pressure of 1 Torr, and then kept at the same temperature for30 minutes so that the solvent was removed therefrom to obtain a lightgreen transparent film. The film thus obtained was then kept at atemperature of 200° C. in the atmosphere for 2 hours. When the materialwas examined for the presence of deposit by X-ray diffractometry, thedeposition of CuBr was observed. This film contained a deposit having asufficiently small grain diameter and thus assumed transparent and lightgreen.

EXAMPLE 31

In a stream of dried nitrogen, 0.236 g of diaminodiphenyletherrepresented by the foregoing general formula (23) was dissolved in 7.5ml of dimethylacetamide. After complete dissolution was made, 0.314 g ofpyromellitic dianhydride represented by the foregoing general formula(24) was gradually added to the solution. Subsequently, in a stream ofdried nitrogen, the mixture was slowly stirred with its temperature keptat 10° to 15° C. for 1 hour. The mixture was further stirred with itstemperature kept at 20° to 25° C. for 2 hours to obtain a solution of ahigh molecular compound represented by the foregoing general formula(25). The high molecular compound solution thus obtained and a turbidcolloidal solution obtained by mixing 0.065 g of CuCl with 7.5 ml ofdimethylacetamide with stirring were mixed. As a result, the solutionturned to a light green transparent liquid in which CuCl had beendissolved. The foregoing mixing procedures were all effected in anatmosphere of dried nitrogen. To the solution thus obtained was thenadded 0.133 g of methyltrimethoxysilane with stirring to obtain auniform solution. To the solution was then added 0.036 g of a 0.05Nhydrochloric acid. The mixture was then stirred at room temperature for6 hours to undergo hydrolysis.

The solution thus obtained as a coating solution was then spin-coated ona quartz glass substrate to form a thin film. The foregoing procedureswere all effected in an atmosphere of dried nitrogen. After dried, thecoated material was heated to a temperature of 80° C. in vacuo under areduced pressure of 1 Torr, and then kept at the same temperature for 1hour to remove the solvent therefrom and accelerate gelatinization toobtain a light yellow transparent crack-free homogeneous film. Theforegoing coating solution was diluted with ethanol three times. Thecoating solution thus diluted was then spin-coated on a crystallinesilicon substrate to form a thin film. This film was heated and dried atthe same time with the foregoing film. These specimens were measured forinfrared absorption spectrum. These specimens were then allowed to coolto room temperature. These specimens were heated to a temperature of200° C. in vacuo under a reduced pressure of 1×10⁻⁵ Torr at a rate of20° C./min. and then kept at the same temperature for 1 hour. Thesespecimens were then allowed to cool to room temperature in vacuo.

The specimen formed on the crystalline silicon substrate was measuredfor infrared absorption spectrum before and after heat treatment toeffect comparison of the change of absorption spectrum. As a result, itwas found that the heat treatment involves the change from the polyamicacid compound represented by the foregoing general formula (25) to thepolyimide compound represented by the foregoing general formula (26). Itwas also found that ethoxy group and hydroxyl group which had beenunreacted before the heat treatment underwent decomposition to causesol-gel reaction. The specimen formed on the quartz glass substrate wassubjected to X-ray diffractometry and absorption spectrometry. As aresult, X-ray diffraction spectrum showed diffraction peaks bymicrocrystal of CuCl, proving that finely divided grains of CuCl can beseparated out in this thin film. Further, when this film was measuredfor absorption spectrum, a CuCl exiton absorption sub-band structure wasfound at around 370 nm. This shows that the material thus prepared canbe applied to a nonlinear optical material.

A section of this thin film was observed under a transmission electronmicroscope. As a result, it was found that this film comprises finelydivided grains of CuCl having a size of 5 to 10 nm uniformly dispersedtherein in a high density.

EXAMPLE 32

A thin film was formed on a quartz glass substrate in the same manner asin Example 31 except that CuBr was used as a starting material of finelydivided grains. The thin film thus obtained was a thin film that assumestransparent and light yellow and is homogeneous and insusceptible tocrack. This film was subjected to X-ray diffractometry, absorptionspectrometry and section observation under a transmission electronmicroscope in the same manner as in Example 1. This film was found tocomprise finely divided grains of CuBr having a size of 5 to 10 nmuniformly dispersed therein in a high density and exhibit absorption ofexcimers of finely divided grains of CuBr. Thus, this thin film can beapplied to a nonlinear optical material.

EXAMPLE 33

1.043 g of tetraethoxysilane (Si(OCH₂ CH₃)₄) was mixed with 2.0 ml ofethanol. The mixture was then mixed with 0.544 g of a 0.05N hydrochloricacid. The mixture was heated to a temperature of 50° C. under reflux for3 hours to obtain a partial hydrolyzate of tetraethoxysilane. To thesolution thus obtained was then added dropwise 1.332 g ofmethyltrimethoxysilane. The mixture was then stirred for 5 hours toundergo hydrolysis. The sol thus obtained was then added to the polyamicacid solution of CuCl obtained in Example 31 to obtain a light yellowtransparent solution. The solution thus obtained as a coating solutionwas then subjected to coating and calcination in the same manner as inExample 31. The thin film thus obtained was a film that assumestransparent and light yellow and is homogenous and insusceptible tocrack.

This film was subjected to X-ray diffractometry, absorption spectrometryand section observation under a transmission electron microscope in thesame manner as in Example 1. As a result, X-ray diffraction peaks wereobserved, showing that finely divided grains of CuCl had been separatedout in the film. The absorption spectrum showed absorption of excimersof finely divided grains of CuCl. Thus, this thin film can be applied toa nonlinear optical material.

Comparative Example 3

2.083 g of tetraethoxysilane was dissolved in 1.5 ml of ethanol. Themixture was then mixed with 0.721 g of a 0.05N hydrochloric acid. Themixture was then heated to a temperature of 50° C. under reflux for 3hours to obtain a partial hydrolyzate of tetraethoxysilane. The solutionthus obtained was then stirred at room temperature for 5 hours toundergo hydrolysis. To the sol was then added a solution of 0.032 g ofCuCl in 2.0 ml of acetonitrile with stirring. The solution thus obtainedas a coating solution was then subjected to coating and calcination inthe same manner as in Example 29. The thin film thus obtained had manycracks thereon and thus were peeled off the substrate, making itimpossible to evaluate the properties thereof.

EXAMPLE 34

To 3.5 ml of dimethylacetamide were added 1.467 g of phthalic anhydride.The mixture was stirred in an ice-water bath until complete dissolutionwas made. To the solution were then added dropwise 2.150 g ofγ-aminopropyltriethoxysilane γ-APS:H₂ N-(CH₂)₃ Si(OCH₂ CH₃)₃ ! withstirring. The mixture was then stirred for 2 hours to undergo reaction.To the solution was then added 0.085 g of CuCl. The mixture was stirreduntil CuCl was completely dissolved to obtain a light blue transparentsolution. To the solution was then added dropwise 0.523 g of a 0.2Nhydrochloric acid. The mixture was then stirred for 5 hours to undergohydrolysis. The dropwise addition of hydrochloric acid caused thesolution to turn to a yellow transparent solution.

The solution thus obtained as a coating solution was then spin-coated ona quartz glass substrate to form a thin film. The foregoing procedureswere all effected in an atmosphere of dried nitrogen. After dried, thecoated material was heated to a temperature of 80° C. in vacuo under areduced pressure of 1 Torr, and then kept at the same temperature for 1hour to remove the solvent therefrom and accelerate gelatinization toobtain a light yellow transparent crack-free homogeneous film. However,the thin film thus obtained was a soft film that can be marked withfingerprint when pressed with a finger. The thin film was measured forthickness by a light interference type thickness gauge at a refrax indexof 1.5. The result was 1.2 μm. The foregoing coating solution wasdiluted with ethanol three times. The coating solution thus diluted wasthen spin-coated on a crystalline silicon substrate to form a thin film.This film was heated and dried at the same time with the foregoing film.These specimens were measured for infrared absorption spectrum.

These specimens were then allowed to cool to room temperature. Thesespecimens were heated to a temperature of 200° C. in vacuo under areduced pressure of 1×10⁻⁵ Torr at a rate of 20° C./min. and then keptat the same temperature for 1 hour. These specimens were then allowed tocool to room temperature in vacuo. The film thus obtained exhibited aninsufficient hardness even after heat treatment such that it can bedamaged when rubbed with a metallic pin.

The specimen formed on the crystalline silicon substrate was measuredfor infrared absorption spectrum before and after heat treatment toeffect comparison of the change of absorption spectrum. FIGS. 7(a) and(b) show infrared absorption spectrum before and after heat treatment,respectively. As a result, it was found that the heat treatment involvesthe change of the matrix from the polysiloxane compound represented bythe following general formula (38) to the polysiloxane compoundrepresented by following general formula (39). It was also found thatethoxy group and hydroxyl group which had been unreacted before the heattreatment underwent decomposition to cause sol-gel reaction. ##STR42##

The specimen formed on the quartz glass substrate was subjected to X-raydiffractometry and absorption spectrometry. FIG. 8 show X-ray spectrumand absorption spectrum, respectively. As a result, X-ray diffractionspectrum showed diffraction peaks by microcrystal of CuCl, proving thatfinely divided grains of CuCl can be separated out in this thin film.Further, the absorption spectrum showed two definite absorption peaks inthe vicinity of 370 nm. These absorption peaks-correspond to theabsorption of excimers of finely divided grains of CuCl. This shows thatthe material thus prepared can be applied to a nonlinear opticalmaterial.

A section of this thin film was observed under a transmission electronmicroscope. As a result, it was found that this film comprises finelydivided grains of CuCl having a size of 5 to 10 nm uniformly dispersedtherein in a high density.

Then, the CuCl fine grain-dispersed thin film thus obtained was measuredwith respect to the nonlinear susceptibility χ.sup.(3) in the samemanner as in Example 7. The value of χ.sup.(3) was very high, 2.5×10⁻⁸esu.

EXAMPLE 35

A thin film was formed on a quartz glass substrate in the same manner asin Example 34 except that CuBr was used as a starting material of finelydivided grains. The thin film thus obtained was a thin film that assumestransparent and light yellow and is homogeneous and insusceptible tocrack. The result was 1.3 μm.

This film was subjected to X-ray diffractometry, absorption spectrometryand section observation under a transmission electron microscope in thesame manner as in Example 34. This film was found to comprise finelydivided grains of CuBr having a size of 5 to 10 nm uniformly dispersedtherein in a high density and exhibit absorption of excimers of finelydivided grains of CuBr. Thus, this thin film can be applied to anonlinear optical material.

Then, the CuBr fine grain-dispersed thin film thus obtained was measuredwith respect to the nonlinear susceptibility χ.sup.(3) in the samemanner as in Example 8. The value of χ.sup.(3) was very high, 4.6×10⁻⁹esu.

EXAMPLE 36

1.250 g of tetraethoxysilane (Si(OCH₂ CH₃)₄) was mixed with 2.0 ml ofethanol and 0.652 g of a 0.5N hydrochloric acid. The mixture was heatedto a temperature of 50° C. under reflux for 3 hours to obtain a partialhydrolyzate of tetraethoxysilane. To the solution thus obtained was thenadded 1.362 g of methyltrimethoxysilane and 1.0 ml of ethanol. To themixture was then added dropwise 0.375 g of a 0.5N hydrochloric acid withstirring. The mixture was then stirred for 5 hours to undergohydrolysis. To the sol thus obtained was then added 2.582 g of the CuClsolution obtained in Example 34 to obtain a light yellow transparentsolution. The solution thus obtained as a coating solution was thensubjected to coating and calcination in the same manner as in Example34. The thin film thus obtained was then measured for thickness in thesame manner as in Example 34. The result was 1.5 μm. The thin film thusobtained was a film that assumes transparent and light yellow and ishomogenous and insusceptible to crack. This thin film had a sufficienthardness such that it could not be visually damaged even when rubbedwith a metal pin after dried.

This film was subjected to X-ray diffractometry, absorption spectrometryand section observation under a transmission electron microscope in thesame manner as in Example 34.

As a result, X-ray diffraction peaks were observed, showing that finelydivided grains of CuCl had been separated out in the film. Theabsorption spectrum showed absorption of excimers of finely dividedgrains of CuCl. Thus, this thin film can be applied to a nonlinearoptical material.

EXAMPLE 37

A thin film was prepared in the same manner as in Example 36 except thatmethyltrimethoxysilane was replaced by ethyltrimethoxysilane CH₃ CH₂Si(OCH₃)₃ !. The thin film thus obtained was then measured for thicknessin the same manner as in Example 34. The result was 1.8 μm. The thinfilm thus obtained was a film that assumes transparent and light yellowand is homogenous and insusceptible to crack. This thin film had asufficient hardness such that it could not be visually damaged even whenrubbed with a metal pin after dried.

This film was subjected to X-ray diffractometry, absorption spectrometryand section observation under a transmission electron microscope in thesame manner as in Example 34.

As a result, X-ray diffraction peaks were observed, showing that finelydivided grains of CuCl had been separated out in the film. Theabsorption spectrum showed absorption of excimers of finely dividedgrains of CuCl. Thus, this thin film can be applied to a nonlinearoptical material.

Comparative Example 4

2.084 g of tetraethoxysilane was mixed with 2.5 ml of ethanol and 0.721g of a 0.5N hydrochloric acid. The mixture was heated to a temperatureof 50° C. under reflux for 3 hours to obtain a partial hydrolyzate oftetraethoxysilane. To the solution thus obtained was then added 0.210 gof an acetonitrile solution of CuCl. The mixture was then stirred. Thesolution thus obtained as a coating solution was then subjected tocoating and calcination in the same manner as in Example 34. The thinfilm thus obtained had many cracks thereon and thus were peeled off thesubstrate, making it impossible to evaluate the properties thereof.Thus, the coating solution was coated on the substrate, and thenimmediately measured for thickness. The result was 1.3 μm (as calculatedat a refrax index of 1.5).

EXAMPLE 38

In a stream of dried nitrogen, 0.236 g of diaminodiphenyletherrepresented by the following general formula (23) and 0.178 g ofdi(aminophenyl)diethoxysilane represented by the following generalformula (40) were dissolved in 10.0 ml of dimethylacetamide. Aftercomplete dissolution was made, 0.472 g of pyromellitic dianhydriderepresented by the general formula (24) was gradually added to thesolution. Subsequently, in a stream of dried nitrogen, the mixture wasslowly stirred with its temperature kept at 10° to 15° C. for 1 hour.The mixture was further stirred with its temperature kept at 20° to 25°C. for 2 hours to obtain a solution of a high molecular compoundrepresented by the following general formula (41) which has an intrinsicviscosity of 0.92 dl/g at a temperature of 30° C. in dimethylacetamide.The solution of a high molecular compound thus obtained and a turbidcolloidal dispersion obtained by mixing 0.065 g of CuCl and 7.5 ml ofdimethylacetamide with stirring were then mixed. As a result, thesolution turned to a light green transparent liquid in which CuCl hadbeen dissolved. The foregoing mixing procedures were all effected in anatmosphere of dried nitrogen. To the solution was then added 0.133 g ofmethyltrimethoxysilane. The mixture was then stirred to obtain a uniformsolution. To the solution was then added 0.036 g of a 0.05N hydrochloricacid. The mixture was stirred at room temperature for 6 hours to undergohydrolysis. ##STR43##

The solution thus obtained as a coating solution was then spin-coated ona quartz glass substrate to form a thin film. The foregoing procedureswere all effected in an atmosphere of dried nitrogen. After dried, thecoated material was heated to a temperature of 80° C. in vacuo under areduced pressure of 1 Torr, and then kept at the same temperature for 1hour to remove the solvent therefrom and accelerate gelatinization toobtain a light yellow transparent crack-free homogeneous film. Theforegoing coating solution was diluted with ethanol three times. Thecoating solution thus diluted was then spin-coated on a crystallinesilicon substrate to form a thin film. This film was heated and dried atthe same time with the foregoing film. These specimens were measured forinfrared absorption spectrum.

These specimens were then allowed to cool to room temperature. Thesespecimens were heated to a temperature of 200° C. in vacuo under areduced pressure of 1×10⁻⁵ Torr at a rate of 20° C./min. and then keptat the same temperature for 1 hour. These specimens were then allowed tocool to room temperature in vacuo.

The specimen formed on the crystalline silicon substrate was measuredfor infrared absorption spectrum before and after heat treatment toeffect comparison of the change of absorption spectrum. As a result, itwas found that the heat treatment involves the change of the polyamicacid compound represented by the foregoing general formula (41) in thematrix to the polyimide compound represented by following generalformula (42). It was also found that methoxy group, ethoxy group andhydroxyl group which had been unreacted before the heat treatmentunderwent decomposition to cause sol-gel reaction. It was further foundthat finely divided grains of CuCl can be separated out in this thinfilm. This shows that the material thus prepared can be applied to anonlinear optical material. A section of this thin film was observedunder a transmission electron microscope. As a result, it was found thatthis film comprises finely divided grains of CuCl having a size of 5 to10 nm uniformly dispersed therein in a high density. ##STR44##

EXAMPLE 39

A thin film was formed on a quartz glass substrate in the same manner asin Example 38 except that CuBr was used as a starting material of finelydivided grains. The thin film thus obtained was a thin film that assumestransparent and light yellow and is homogeneous and insusceptible tocrack.

This film was subjected to X-ray diffractometry, absorption spectrometryand section observation under a transmission electron microscope in thesame manner as in Example 38. This film was found to comprise finelydivided grains of CuBr having a size of 10 to 20 nm uniformly dispersedtherein in a high density and exhibit absorption of excimers of finelydivided grains of CuBr. Thus, this thin film can be applied to anonlinear optical material.

This film was subjected to X-ray diffractometry, absorption spectrometryand section observation under a transmission electron microscope in thesame manner as in Example 34.

As a result, X-ray diffraction peaks were observed, showing that finelydivided grains of CuCl had been separated out in the film. Theabsorption spectrum showed absorption of excimers of finely dividedgrains of CuCl. Thus, this thin film can be applied to a nonlinearoptical material.

EXAMPLE 40

A thin film was formed on a quartz glass substrate in the same manner asin Example 38 except that the polyamic acid compound represented by thefollowing general formula (44) synthesized from a compound representedby the following general formula (43) was used instead of the compoundrepresented by the foregoing general formula (40). The thin film thusobtained was a thin film that assumes transparent and light yellow andis homogeneous and insusceptible to crack.

This film was subjected to X-ray diffractometry, absorption spectrometryand section observation under a transmission electron microscope in thesame manner as in Example 38. This film was found to comprise finelydivided grains of CuCl having a size of 5 to 20 nm uniformly dispersedtherein in a high density and exhibit absorption of excimers of finelydivided grains of CuCl. Thus, this thin film can be applied to anonlinear optical material. ##STR45##

Comparative Example 5

2.084 g of tetraethoxysilane was mixed with 2.5 ml ethanol and 0.721 gof a 0.5N hydrochloric acid. The mixture was heated to a temperature of50° C. under reflux for 3 hours to obtain a partial hydrolyzate oftetraethoxysilane. The solution thus obtained was then stirred at roomtemperature for 5 hours to undergo hydrolysis. To the sol thus obtainedwas then added 0.209 g of an acetonitrile solution of CuCl. The mixturewas then stirred. The solution thus obtained as a coating solution wasthen subjected to coating and calcination in the same manner as inExample 38. The thin film thus obtained had many cracks thereon and thuswere peeled off the substrate, making it impossible to evaluate theproperties thereof.

EXAMPLE 41

In a stream of dried nitrogen, 0.572 g of diaminodiphenyletherrepresented by the following general formula (23) was dissolved in 20 mlof dimethylacetamide. After complete dissolution was made, 0.628 g ofpyromellitic dianhydride represented by the general formula (24) wasgradually added to the solution. Subsequently, in a stream of driednitrogen, the mixture was slowly stirred with its temperature kept at 10to 15° C. for 1 hour. The mixture was further stirred with itstemperature kept at 20° to 25° C. for 2 hours to obtain a solution of ahigh molecular compound represented by the general formula (5). To thesolution of a high molecular compound was added 0.20 g of ZnCl₂ withstirring to obtain a light-yellow clear liquid.

The thus obtained solution was spin-coated or a glass substrate andheated at 70° C. for 30 minutes in vacuo to remove the solvent, wherebya light-yellow transparent film was obtained. The film was thensubjected to a heat treatment at 250° C. for one hour in a stream of amixed gas of O₂ and H₂ O at the rate of 100 ml/min. The mixed gas wasobtained by bubbling oxygen gas in water. An X-ray diffractometry of thetreated film revealed that finely divided grains of ZnO wereprecipitated in the film. The grain size of the precipitate was 5 to 50nm when measured with a transmission electron microscope. As the ZnOgrains were small so that the resulting film was transparent andappeared light-yellow.

As mentioned above, the nonlinear optical material according to thepresent invention comprises finely divided grains of a semiconductor ormetal which have been separated out by the change of functional groupsin a matrix, which finely divided grains being dispersed therein. Thus,when coated on a substrate to form a thin film, it provides a nonlinearoptical element having a sufficient thickness that is insusceptible tocrack and exhibits a high nonlinear optical effect. Further, thenonlinear optical material according to the present invention cancomprise finely divided grains of a semiconductor or metal having anonlinear optical effect stably retained in a high molecular compound oranalogy to glass in a high concentration, making it possible to providea material which exhibits a high nonlinear optical effect and mechanicalstrength and an excellent optical transparency.

Accordingly, the nonlinear optical material according to the presentinvention can be effectively used in the field of optoelectronics. Thatis, it can be used as photo switch or photo memory or for wavelengthconversion, automatic correction of optical system or light computing.

In the present invention, a nonlinear optical material can be preparedat a low temperature, making it possible to provide a material which caneasily decompose or evaporate on heating. Further, since a functionalgel can be prepared beginning with the solution state, no complicatedpreparation procedures are required, making it easy to change the shapeof the gel. Thus, in accordance with the present invention, thenonlinear optical material can be formed into any shape such as film,plate, block and fiber.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A process for the preparation of a nonlinearoptical element that gives a nonlinear response to incident light,comprising:mixing a solution of a matrix-forming substance containing afunctional group with a metal, a semiconductor or precursor thereof toform a uniform solution, accelerating dissolution of said metal,semiconductor or precursor by interaction with said functional group;reducing or eliminating said interaction between said functional groupand said metal, semiconductor, or precursor to form a matrix whileprecipitating finely divided grains of said metal or semiconductor insaid matrix.
 2. The process for the preparation of a nonlinear opticalelement according to claim 1, wherein the reaction of a functional groupis an imide ring formation reaction.
 3. The process for the preparationof a nonlinear optical element according to claim 1, wherein thereaction of a functional group is an acid addition salt formationreaction by the acid treatment of an amino compound.
 4. The process forthe preparation of a nonlinear optical element according to claim 1,wherein as said matrix-forming substance containing a functional groupthere is used a high molecular compound containing a repeatingstructural unit represented by the following general formula (9):##STR46## wherein X represents a tetravalent organic group having notless than 2 carbon atoms; and Y represents a divalent organic grouphaving not less than 2 carbon atoms.
 5. The process for the preparationof a nonlinear optical element according to claim 1, wherein as saidmatrix-forming substance containing a functional group there is used atleast one high molecular compound containing in its side chain orcrosslinked moiety an amide acid structure represented by any one of thefollowing general formulae (10) to (12): ##STR47## wherein X representsa tetravalent organic group having not less than 2 carbon atoms; Yrepresents a divalent organic group having not less than 2 carbon atoms;W represents an organic group having not less than 2 carbon atomsnecessary for the formation of an imide ring; and Z represents an alkyl,aryl or aralkyl group.
 6. The process for the preparation of a nonlinearoptical element according to of claim 1, wherein said finely dividedgrains of a semiconductor are finely divided grains of cuprous halide.